Highlights of Joint ResearchInternational Conferences and Workshops
ISSP Workshops

Highlights of Joint Research

Synchrotron Radiation Laboratory
The Synchrotron Radiation Laboratory (SRL) was established in 1975 as a research group dedicating to solid statephysics using synchrotron radiation. In 1989, the SRL started
to hold the Tsukuba branch, a branch laboratory in the
Photon Factory (PF), High Energy Accelerator Research
Organization (KEK). SRL maintains an undulator called
Revolver, two beamlines and three experimental stations;
BL-18A for angle-resolved photoemission spectroscopy andundulator beamlines, BL-19A and BL-19B for spin-resolved
photoelectron spectroscopy and soft X-ray emission
spectroscopy experiments, respectively. They are fully
opened to outside users for experiments using high brilliant
synchrotron radiation from the undulator. The operation timeof these beamlines are about 5000 hours and the number ofusers is more than 200 a year.
The present SRL consists of the accelerator physics
group and the solid state spectroscopy group. The membersof the accelerator group have been carrying out researchworks on the accelerator physics and developing various new
accelerator related technology in collaboration with other SR
facilities. The spectroscopy group has been not only serving
users at the Tsukuba branch with technical supports andadvices, but also carrying out their own research works on
advanced solid state spectroscopy.
In 2005, the operation of PF ring was quitted for six
months to improve its characteristics as a light source.
During this long-term shut down of PF, the staff members of
SRL improved experimental apparatuses at the beamlines,
which results some new achievements. They installed a newhigh resolution electron energy analyser (PHOIBOS 150)
and an equipment for sample preparation at BL-19A. The
new system is combined with high efficiency spin detector
utilizing very low energy electron diffraction (VLEED)
technique. After the completion of the new system, theapparatuses will be opened for spin-resolved photoemission
experiments with a high energy resolution of several 10 meV

Fig. 1. Schematics of the undulator beamline at SPring-8

36

ISSP Activity Report 2006

and a figure of merit larger than 10-3 in the spin analysis.
Since 1980s, SRL has been promoting the “Super-SOR”
project for constructing a new synchrotron radiation facility
with a third generation light source dedicated to the sciencesin vacuum ultraviolet and soft X-ray (VSX) regions.
However, in 2005 the president office of the University ofTokyo found out that the promotion of the project is very
difficult since the budget for the new project is too big to besupported by a single university in Japan even after the reformation of the national universities. After many severe
discussions, SRL has inclined to construct beamlines using
undulator radiation in other SR facilities instead of
constructing the facility with a light source and to promoteadvanced materials sciences using high brilliance and small
emittance of SR which have been considered in the SuperSOR project.
In October 2006, the president office decided to promoteresearch activities of the University of Tokyo using SR, andunified them under a new group, the Synchrotron Radiation
Research Organization (SRRO) of the University of Tokyo.
The new Organization consists of two divisions, Materials
Science Division and Life Science Division. The staff
members of SRL, the solid state spectroscopy group will
participate to the Materials Research Division and playessential roles in promoting scientific activities using SR.
The University also supports them financially and she will beready to prepare the budget for the construction of new
beamlines in existing SR facilities. SRRO is planning toconstruct a new 25m-long undulator at SPring-8. They also
proposed new beamlines and experimental equipments using
high brilliance synchrotron radiation in soft X-ray region.
They are those for soft X-ray microscopy experiments, timeresolved experiments which will only be possible using third
generation light source and will promise us a considerable
progress in the studies of nano-particles and real time observation of magnetic domains and of chemical reaction at
catalytic surfaces, etc.
The accelerator group started to study ERL(energy
recovery linac)-based light sources and develop ERL components in collaboration with KEK and JAEA. A nine-cellsuperconducting cavity was designed for high current ERLs
and will be fabricated and tested in 2007. A high-power
input coupler with two ceramic windows and a novel HOMdamped structure for suppression of both dipole and quadrupole modes are also being designed for the cavity.
Furthermore multi-bunch beam break-up due to long-range
resistive-wall wake-fields that could be a serious problem forhigh-current ERLs was intensively investigated to fully
understand and cure it. They also developed several
advanced components and methods related to light source
accelerators. A copper-coated stainless-steel vacuum
chamber was experimentally demonstrated to work wellunder the ultra-high vacuum and its copper-coating
technique was adopted for a new BL-16 undulator chamberat KEK-PF to keep the beam stable by reducing the resistive-

wall wakefield. A pulse sextupole magnet for normal andtop-up injections was designed and confirmed by simulations
to inject the beam into the PF-ring without serious beam loss.
A digital beam position monitor system was developed tostabilize low-emittance beam positions with high resolution
and flexibility. Its performance test was successfully carriedout with a test bench at ISSP and then the system was also
demonstrated by a beam test at KEK-LINAC to be useful forsingle-pass beam position measurements.

surface, slow dynamics of surfactants, pressure dependenceof dynamics of amphiphilic membranes, and so on. In
addition, there are a variety of activities on fundamental
physics, neutron beam optics, developments of neutron
scattering techniques.
The NSL also operates the U.S.-Japan cooperative
program on neutron scattering, providing further research
opportunities to material scientists who utilize the neutron
scattering technique for their research interests.
The details of individual studies and research highlights
in JFY2006 will be reported in the NSL-ISSP Activity
Report vol. 14.

Neutron Science Laboratory
The Neutron Science Laboratory (NSL) has been playing
a central role in neutron scattering activities in Japan since
1961 by performing its own research programs as well as
providing a strong general user program for the universityowned various neutron scattering spectrometers installed at
the JRR-3 operated by Japan Atomic Energy Agency inTokai. In 2003, the Neutron Scattering Laboratory was
reorganized as the Neutron Science Laboratory to further
promote the neutron science with use of the instruments in
JRR-3. Under the general user program supported by NSL,
14 university-group-owned spectrometers in the JRR-3
reactor (20MW) are available for a wide scope of researches
on material science, and proposals close to 300 are submitted
each year, and the number of visiting users under thisprogram reaches over 6000 person-day/year.
Triple axis spectrometers and a high resolution powder
diffractometer are utilized for a conventional solid statephysics and a variety of research fields on hard-condensed
matter, while in the field of soft-condensed matter science,researches are mostly carried out by using the small angle
neutron scattering (SANS-U) and/or neutron spin echo
(iNSE) instruments. The upgraded time-of-flight (TOF)
inelastic scattering spectrometer is now opened to the user
proposals.
Major research topics on the hard-condensed matterscience cover stripe order in high-Tc superconductors, andclosely related 2 dimensional systems, charge and orbital
ordering in CMR manganites, quadrapolar ordering in rareearth based intermetallic compounds, spin dynamics of low
dimensional dimmer systems, etc. On the other hand, theresearch topics on the soft-condensed matter science cover
structural characterization of polymer blends, micelles,
amphiphilic polymers block copolymers, liquid crystals,
proteins, inorganic gels, dynamics of brush-polymers on

Supercomputer Center
The mission of the Supercomputer Center of the Institute(SCC-ISSP) is to serve the whole community of computational condensed-matter physics in Japan providing it withhigh performance computing environment. The mission isachieved through the User Programs supervised by theMaterials Design and Characterization Laboratory (MDCL).
One of our specific goals is to selectively promote andsupport large-scale computations.
The center operates two super-computers, systems A andB, which were renewed in March 2005. System A is Hitachi
SR11000/48 that consists of 48 high performance nodes
composed of tightly-coupled microprocessors. A node can beused as if it were a single-processor computer by automaticparallelization of its FORTRAN compiler. System A has
2.8 TB memory and archives 5.8 TFlops peak performancein total. On the other hand, System B, which is SGI Altix
3700/1280, is a loosely-coupled parallel supercomputerconsisting of 19 nodes inter-connected by a gigabit Ethernet
network. Each node is a distributed-shared-memory-typecomputer consisting of 64 Intel Itanium 2 CPUs interconnected by a rather high performance network and have 64
GB memory. System B achieves 7.7 TFlops total throughput
performance.
Any staff member of university faculties or publicresearch institutes in Japan can apply for a project of theUser Program. Proposals are evaluated by the Steering
Committee of the center, under which the Supercomputer
Project Advisory Committee is formed to review proposals
in detail. In fiscal year 2006 totally 184 projects wereapproved. The total points applied and approved are listed inTable. 1 below.
========================================================Class Max/Min Application
Point

# of

Total points (K points)

Proj.

AppliedSys-A

Approved

Sys-B

Sys-A

Sys-B

------------------------------------------------------------------------------------------------------A<100K

any time

2

150

50

150

50

B

<2M

twice a year

52

60100

39350

57600

38250

C

<20M

twice a year

112

1176200

757200930700684500any time

17265000218000173400177000

twice a year

1

0

70000

0

70000

184

15014501084600

1161850969800

D
S
Total

>20M

========================================================

Fig. 1. The reactor hall of JRR-3. The eight neutron scattering instruments are attached to the horizontal beam tubes in the reactor experimental hall. Two thermal and three cold guides are extracted from thereactor core towards the guide hall located to the left.

Table 1. Research projects approved in 2006.
The maximum points allotted to the project of each class are the sumof the points for the two systems. 1 K points of System-A correspondto charge for 0.37 hours × node, while the corresponding figure is 0.22
hours × node for System-B.

ISSP Activity Report 2006

37

The research projects are roughly classified into thefollowing three categories (the number of projects
approved):
First-Principles Calculation of Materials Properties (71)
Strongly Correlated Quantum Systems (66)
Cooperative Phenomena in Complex, Macroscopic
Systems (47)
All the three involve both methodology of computationand its applications. The results of the projects are reported
in 'Activity Report 2006' of the SCC-ISSP. In the report thefollowing four invited articles are included:"Giant Intrinsic Spin Hall Effect in Transition Metal
Compounds", by H. Kontani, T. Tanaka, D. S. Hirashima,
K. Yamada, and J. Inoue,"Fluctuations near Quantum Critical Points of Valence
Transition and Superconductivity", by S. Watanabe,"A First-principles Investigation on the Mechanism of
Nitrogen Dissolution in the Na Flux Method", by
M. Kawahara, S. Yanagisawa, and Y. Morikawa,"Chaos Effect in the Edwards-Anderson Ising Spin Glass:
A numerical Domain Wall Renormalization-Group
Study", by M. Sasaki, K. Hukushima, H. Yoshino, and
H. Takayama.

involve magneto-optical measurements, cyclotron resonance,
spin resonance, magnetization and transport measurements.
Our interests cover the study on quantum phase transitions (QPT) induced by high magnetic fields. Field-induced
QPT has been explored in various materials such as quantum
spin systems, strongly correlated electron systems and othermagnetic materials. Non-destructive pulsed fields enable us
to measure many kinds of materials precisely. The number ofcollaborative groups for the research is over 30 in the year of
2006. Multiple extreme physical conditions combined withultra-low temperatures and ultra-high pressures are alsoavailable. The magnet technologies are intensively devoted
to the quasi-steady long pulse magnet (an order of 1-10 sec)energized by the giant DC power supply, and also to a 100
Tesla nondestructive magnet.
Our destructive magnets, such as the single-turn coil andthe electro-magnetic flux compression (EMFC) systems,
would be oriented toward easier access and more reliablemeasurements for solid-state physics than previously obtainable. One of our recent successes was the achievement ofover 630 T within a 3.8 MJ energy injection by the EMFC, inwhich a new type of primary coil with a simpler design was
employed. These are oriented for developing new horizons inmaterial science realized under such extreme quantum limit
conditions.

International MegaGauss
Science Laboratory
The mega-gauss facility at the Institute for Solid State
Physics has decided to introduce a 210 MJ flywheel generator which is the world largest DC power supply (recorded in
Guinness book of records in 1907/98) for generation of thelong-pulse magnetic field, and to transfer it from Naka
Fusion Institute, Japan Atomic Energy Agency. The DC
power generator finished its role of supplying energy into the
Toroidal magnetic field coil in JFT-2M (JAERI Fusion
Torus-2M) tokamak nuclear fusion testing device in 2004.
In accordance with this decision, which is recommended
by the High Magnetic Field Forum Japan, we have changed
the structure of our organization of the previous group andnamed it the “International MegaGauss Science Laboratory(IMGSL)”. This laboratory started from 2006 fiscal year.
The aim of this laboratory is to study the physical properties of solid-state materials (such as semiconductors,
magnetic materials, metals, insulators, superconducting
materials) under ultra-high magnetic field conditions. Such ahigh magnetic field is also used for controlling the newmaterial phase and functions. Our pulse magnets, at moment,
can generate up to 80 Tesla by non-destructive manner (theworld record), and from 100 up to 630 Tesla (the worldstrongest as an in-door record) by destructive (the single turn
coil and the electro-magnetic flux compression) methods.
They are opened to scientists both from Japan and fromoverseas, especially from Asian countries, and many fruitfulresults are expected to come out not only from collaborative
research but also from our in-house activities. One of ourultimate goals is to provide the scientific users as our joint
research with magnets capable of a 100 T, milli-second
pulses in a non-destructive mode, and to offer physical precision measurements. The available measuring techniques now

38

ISSP Activity Report 2006

Fig. 1. Entrance signboards of the new International MegaGauss
Science Laboratory. The fly-wheel generator which is the world largest
DC power supply for non-destructive pulse magnets aiming at generating 100 Tesla (right bottom). Birds-eye-view of the long-pulse
magnet building in which the fly-wheel generator with magnet stations
are to be installed (left bottom).

NMR Evidence for a Totally Symmetric
Order Parameter in PrFe4P12
J. Kikuchi and M. Takigawa
Intermetallic compounds with the filled-skutterudite
structure RT4X12 (R = rare earth, T = transition metal, X =pnictogen) has attracted strong recent attention because of avariety of intriguing phenomena in a common crystal structure (Fig. 1 left) such as metal-insulator transitions, multipole
orders, exotic superconductivity, and anomalous phonons[1]. Among them, PrFe4P12 shows a peculiar phase transition
at TA=6.5K. The low temperature (T) phase has no spontaneous magnetic moment at zero field and is suppressed by amagnetic field of 4 - 7 T depending on the field directions(Fig. 1 right). The low-T phase has a structural modulation
with the wave vector Q=(1,0,0), indicating loss of t(1/2, 1/2,
1/2) translation. Distinct electronic states for two Pr3+ ions in
the bcc unit cell observed by resonant X-ray scattering, thefield-induced staggered magnetization observed by neutron
scattering, and elastic anomalies have all suggested an
antiferro-quadrupole order likely to be of Γ23-type. However,direct identification of the order parameter has not been
made yet.
We have performed nuclear magnetic resonance (NMR)
experiments on 31P nuclei for microscopic understanding of
the low-T ordered phase [2]. We observed that all NMR lines
in the high-T phase split into two upon entering into the lowT phase (Fig. 2) irrespective of the field direction. This

Fig. 1. Crystal structure (left) and the phase diagram (right) of
PrFe4P12.

Fig. 3. (left) The angle dependence of the NMR line splitting in the
low-T phase (T=4.2 K, H=1.6 T). The lines are fitting to the phenomenological model described in ref. [3]. (right) Schematic illustration of a
totally symmetric hexadecapole moment. Note that the cubic symmetry
is preserved in spite of a highly anisotropic charge distribution.

should be ascribed to the distinction between two P12 cages
surrounding Pr sites at the corner and the body center of theoriginal bcc lattice. Absence of any additional line splitting
indicates that the 4f-electronic charge distribution of each Pr
sites preserves the Th point symmetry of the high-T phase.
From group theoretical arguments [3] and phenomenologicalfitting of the angle dependence of the splitting (Fig. 3 left)[4], we have established that the order parameter belongs to
the totally symmetric Γ1 representation, ruling out any typeof quadrupole order. The line splitting vanishes as themagnetic field is reduced to zero, indicating that the primaryorder parameter at zero field is electric, that is even-rank
multipole moments. For Pr3+, the lowest order totallysymmetric even-rank multipole is the hexadecapole shown in
Fig. 3 (right).
What is the driving force for such a peculiar order ? Ahint is provided by the band structure calculation showing anesting feature of the conduction band with Q=(1,0,0) [4]. It
is well known that electron-lattice coupling in the presenceof Fermi surface nesting leads to a charge density wave
order. A similar Fermi surface instability can be induced bycoupling between conduction electrons and 4f multipole
moments. PrFe4P12 may be an example of such a novel typeof order.
References[1] Y. Kuramoto, JPJS Online-News and Comments [Apr. 13, 2007].
[2] J. Kikuchi, M. Takigawa, H. Sugawara, and H. Sato, J. Phys. Soc.
Jpn. 76, 043705 (2007) (Selected for JPSJ Editor's Choice).
[3] O. Sakai, J. Kikuchi, R. Shiina, H. Sato, H. Sugawara,
M. Takigawa, and H. Shiba, J. Phys. Soc. Jpn. 76, 024710 (2007).
[4] H. Harima and K. Takegahara, J. Phys.: Condens. Matter 15, S2081(2003).
Authors
J. Kikuchia, M. Takigawa, H. Sugawarab,c, H. Satoc, O. Sakaic,
R. Shiinac, and H. Shibad,
aDepartment of Physics, Meiji University
bFaculty of Integrated Arts and Science, University of Tokushima
cGraduate School of Science, Tokyo Metropolitan University
dThe Institute of Pure and Applied Physics

Fast Molecular Transport in Hydrogen
Hydrates by High-Pressure Diamond
Anvil Cell NMR
T. Okuchi, M. Takigawa, and T. Yagi
Fig. 2. (left) 31P NMR spectra at T=50 K. The numbers indicate assignment of each peak to the P sites (P1 - P6, see Fig. 1 left). (right) 31P
NMR spectra at 6.0 K (above TA) and at 4.6 K (below TA) for the fieldof 1.6 T along [111]. NMR peaks from P1, P3, and P5 sites (P2, P4 andP6 sites) are shown by solid (open) circles.

Properties of molecular materials change with pressures.
At several to several tens of gigapascal, chemical bonding
may transform its fundamental nature. Water ices and gas

ISSP Activity Report 200639

hydrogen hydrates [2]. These hydrates have the structures of
ice II and Ic , hence they are called as filled ice hydrates. The
filled-ice II hydrate (C1) is stable to 3 GPa with a composition H2:H2O = 1:6. The filled-ice Ic hydrate (C2) is stable toat least 60 GPa with H2:H2O = 1:1.
In situ proton NMR spectra of these filled-ice hydrogenhydrates at pressures reveal fast translational motion of theH2 molecules enclosed within the ice frameworks. The NMR
spectra to 3.6 GPa gave sharp resonances of the H2 guests,
revealing liquid-like mobile nature of the guest H2 (Fig. 1).
Pressure effects on T1-1 and T2-1 of the H2 indicate thatmolecular rotation and diffusion contribute together to thespin relaxation, from which two motional correlation times
τrot and τdif of the guest H2 were determined separately(Fig. 2). A liquid-like large diffusion coefficient of the H2with little pressure sensitivity was deduced from τdif,
indicating that the ice framework allows active guest translation even in extensively compressed states.
References[1] T. Okuchi, Phys. Earth Planet. Inter. 143-144, 611 (2004).
[2] W. L. Vos, L. W. Finger, R. J. Hemley, and H. K. Mao, Phys. Rev.
Lett. 71, 3150 (1993).
[3] T. Okuchi, M. Takigawa, J. Shu, H. K. Mao, R. J. Hemley, andT. Yagi, Phys. Rev. B. 75, 144104 (2007).
Fig. 1. Solid-echo powder NMR spectra at 300 MHz and optical micrograph of the hydrogen hydrates synthesized within the diamond anvil
cell at high pressures. For each figure, the upper part shows theobserved spectrum and its fitting curve, the middle part shows model
fitting peaks, and the lower part shows the residual. (a) The filled-ice IIphase. (b) The mixture of filled-ice Ic and pure ice VII phases. The L1
peak shows highly-mobile H2 guest molecules enclosed within the ice
frameworks. The L2 and G1 peaks show moderately mobile and static H
species within the H2O framework.

hydrates are typical examples that involve flexible hydrogenbonding phenomena and, therefore, particularly sensitive tothe pressure. Their structure and transportation properties atthis pressure regime are not only important by itself but also
giving implications for internal structure and material transport of icy giant planets and icy satellites in the solar system.
We investigated hydrogen hydrates which are typicalexamples of these ice materials, using a novel method toanalyze both molecular structure and motion at highpressure-high-resolution diamond-anvil-cell nuclear magnetic
resonance spectroscopy [1].
A distinct feature of H2 is its smallest size among themolecules. It is smaller than intrinsic interstices of some ice
polymorphs. At pressures higher than 0.4 GPa, H2 spontaneously dissolve into these ice frameworks to produce dense

Fig. 2. Two motional correlation times (τrot and τdif) and diffusion
coefficient (DG) of the guest H2 molecules. They are determined frompressure and frequency dependences on T1-1 and T2-1 of the guest H2.

40

ISSP Activity Report 2006

Authors
T. Okuchia, M. Takigawa, J. Shub, H. K. Maob, R. J. Hemleyb, andT. YagiaNagoya University
bCarnegie Institution of Washington

Localization Problem in the
Quasiperiodic System with the Spin
Orbit Interaction
M. Kohmoto, D. Tobe, and C. Wexler
The quasiperiodic systems are intermediate between
periodic and random. Electronic states are always extended
in periodic systems. In one dimension, states are always
localized in random systems. The one-dimentional quasiperiodic systems show various interesting wave function andenergy spectral character [1].
We study one-dimensional quasiperiodic system obtained
from the tight-binding model on the square lattice in a
uniform magnetic field with the spin orbit interaction. The
problem involves a Hamiltonian:where λR is the Rashba spin orbit coupling. The phase
diagram with respect to the Harper coupling and the Rashba
coupling are proposed from a number of numerical studies
including a multifractal analysis. (Fig.1).
There are four phases, I, II. III, and IV in this order fromweak to strong Harper couplings. In the weak coupling phase
I all the states are extended, in the intermediate couplingphases II and III mobility edges exist and accordingly localized and extended states coexist, and in the strong Harper
coupling phase IV all the states are localized. Phases I and
IV are related by the duality and also phases II and III are
related by the duality. A localized state is related to an
extended state by the duality and vice versa. The boundaryFig. 1. Proposed phase diagram. The critical line between II and III is
λH ≡ ty / tx = 1.

-

Fig. 2. Plots of the wave functions with σ = ↑ on the self-dual criticalline (a) at the edge of the spectra, (b) at the center of the spectra.
(λH , λR) = (1.0,1.0). q = F19 = 6795.

between phases II and III is the self-dual line on which all
the states are critical. Our result gives a counter example ofthe proof of pure spectrum by Aubry duality. Critical wave
functions on the self-dual critical line are shown in Fig. 2.
References[1] H. Hiramoto and M. Kohmoto, Int. J. Mod. Phys. B 6, 281 (1992).
Authors
M. Kohmoto, D. Tobe, and C. Wexlera
aUniversity of Missouri-Columbia

A Constrained First-Principles
Molecular Dynamics Approach toElectron-Transfer Reactions in Solution

Fig. 1. Helmholtz free energy profile of the redox reaction, RuO4 +H2O + e- → [RuO3(OH)2]2-. The symbols, ξ and θ, denote the reaction
coordinates with respect to the chemical bond change (between tetrahedral and trigonal-bipyramidal forms) and the electron transfer (between
oxidised and reduced states), respectively. The overall reaction freeenergy is calculated to be -0.65 eV, which is in good agreement withthe experimental value (-0.59 eV). Owing to the lower activation freeenergy, the reaction pathway via RuO42- is more favourable than thatthrough [RuO3(OH)2]-.

principles of quantum mechanics and statistical physics only,
it should be applicable under much broader contexts.
We have applied it to a water cleavage reaction coupled
to electron transfer on a transition metal oxide ion in aqueous
solution and demonstrated that it can well reproduce theexperimentally determined free-energies. The resultant freeenergy profile is shown in Fig. 1. We consider that this will
open new perspectives for first-principles investigation ofelectron transfer reactions coupled to chemical bondbreaking/formation.
References[1] Y. Tateyama, J. Blumberger, M. Sprik, and I. Tavernelli, J. Chem.
Phys. 122, 234505 (2005).
[2] Y. Tateyama, J. Blumberger, T. Ohno, and M. Sprik, J. Chem.
Phys. 126, 204506 (2007).
Authors
Y. Tateyamaa
aNational Institute for Materials Science

Y. Tateyama
Chemical reactions with electron-transfer in solution, so
called “redox reactions”, play crucial roles in diverse topics
such as battery, fuel cell, catalysis, corrosion, photosynthesis.
Fundamental aspects of redox reactions are usually characterized by free-energies. Free-energies have been intensively
calculated using the constrained first-principles molecular
dynamics (FPMD) methods, but those methods assume thatthe number of electrons is unchanged during the reaction andthe surrounding bond network is only weakly perturbed by
the reaction. Therefore they cannot be applied to the redox
reactions.
To generalize the constrained FPMD method and makethe redox reactions a target of the study, we have developed
novel computational methods [1, 2]. In particular, the ‘(bluemoon ensemble) constrained FPMD energy gap method’ [2]can deal with free-energy difference between the states withdifferent charges as well as the different chemical bond
networks taking thermal fluctuations of solute and solvent
into account. Since the method is derived using fundamental

An Atomic Seesaw Switch for OneDimensional Electrons on Ge (001)
A. Ishii and F. Komori
Reversible switching of electronic conduction throughatom manipulation is one of the main subjects ofnanoscience. However, different conducting pathways havenot been clearly observed with atomic resolution. We
demonstrate the correlation between the change of surface
atomic position and that of the reflection of one-dimensional(1D) surface-state electrons on the Ge (001) surface with alow coverage of Sn atoms [1].
On the clean Ge(001) surface, two atoms form a buckled
dimer, and bonding π- and antibonding π*-states localize on
upper and lower atoms of the dimer. The Ge dimers align inthe [110] direction and form a dimer row. The π*-electron
behaves like a 1D free electron along the dimer row(see Fig. 1). The buckling orientation of the Ge dimer can bereversibly controlled by surface bias voltage of STM below

ISSP Activity Report 200641

structure of the heterogeneous dimers is estimated. The moststable structure is the buckled dimer with the Sn atom at theupper dimer position (U dimer). The energy of the dimer
with the Sn atom at the lower dimer position (L dimer) is 60
meV higher than the ground state.
An atomic seesaw switch is realized for the 1D π*electrons in the Ge dimer-row direction by using STM to flip
reversibly the buckling orientation of a single Sn-Ge dimerin the dimer row at 80 K. When the Sn atom of the heterogeneous dimer is at the lower position (L dimer), the 1D
electrons are reflected and a standing wave of this state isobserved in the dI/dV image as in Fig. 1(b). Whereas, when
it is at the upper position (U dimer), the 1D electrons passthrough the heterogeneous dimer, and no standing wave isobserved as in Fig. 1(e). In this state, the lower atom of the
dimer is Ge, and the π* state of the dimer is little different
from that of the Ge-Ge dimers.
Fig. 1. (a,b) Topographic (a) and dI/dV (b) images of the Ge(001)surface with L dimer at 80 K. The L dimer is imaged as a protrusion in
the topographic image, and a standing wave is observed around the L
dimer in the dI/dV image. (c) Schematic illustration showing the π*electrons (green line) , which conduct on the lower atoms of the Ge
dimers in the dimer row directon [110], are reflected by the Sn atom
(small blue ball) at the lower dimer position. Red balls indicate the Geatoms. Large balls are the upper dimer atoms, and small ones the lower.
(d,e) Topographic (d) and dI/dV (e) images of the Ge(001) surface with
the U dimer at 80 K. The U dimer is imaged as a protrusion in the
topographic image while no standing wave is observed around the U
dimer in the dI/dV image. (f) Schematic illustration showing the π*electrons (green line) can go through the Sn-Ge dimer. The Sn atom
(large blue ball) at the upper dimer position little affects the π*-electron
conduction.

80 K [2].
When Sn atoms are deposited on the clean Ge(001)surface at room temperature, buckled dimers originatingfrom the Sn atoms are formed at the Ge dimer position in thesurface [3]. The contrast of the STM dimer image at 80 Kchanges by reversing its buckling orientation as shown in
Fig. 2. Thus, it is identified as a heterogeneous Sn-Ge dimer.
On the basis of first-principles calculations, the optimized

Fig. 2. (a-d) Filled ( Vb = – 0.5 V) and empty ( Vb = + 0.5 V) state
STM images for the Sn-Ge dimers with the Sn atom at the upper (Udimer) and lower (L dimer) positions on the Ge(001) surface. Brightly
imaged protrusions indicating the Sn-Ge dimer are seen in (a,b,d) while
its image is the same as the Ge-Ge dimer in (c). Local superstructure of
the surface changed by reversing the buckling orientation of the Sn-Ge
dimer. (e) Structural models of the U dimer and the L dimer. Theenergy of the L dimer is 0.06 eV higher than that of the U dimer.

42

ISSP Activity Report 2006

References[1] K. Tomatsu et al., Science 315, 1696 (2007).
[2] Y. Takagi et al., J. Phys. Soc. Jpn. 72, 2425 (2003).
[3] K. Tomatsu et al., Surf. Sci. 601, 1736 (2007).
Authors
K. Tomatsu, K. Nakatsuji, T. Iimori, Y. Takagi, H. Kusuharaa,
A. Ishiia, and F. Komori
aDep. Appl. Math. and Phys., Tottori University

STM and STS Studies of a
Surface-new-material: Silicon Oxynitride
Ultrathin Film Formed on 6H-SiC(0001)
H. Tochihara and F. Komori
Uniform, abrupt interface between insulating layer andsemiconductor surface has been a long-standing requirement
for progress of electronic devices. Silicon carbide (SiC) is apromising semiconductor for next-generation power devices
due to its fundamental properties [1]. However, oxides/SiC
interface produced by conventional methods has a variety ofdefects with high concentration. Very recently, Shirasawa et al.
have succeeded to prepare a dangling-bond-free, ordered

Fig. 1. Top and side views of ball and stick model of the SiON film on
6H-SiC(0001).

almost the same value of band gap as that of bulk SiO2,~9 eV. This is probably due to a strong resemblance of structural parameters such as Si-O bond length and Si-O-Si bondangle between the silicate layer of the SiON and SiO2
crystals. This fact suggests that underlying silicon nitride
single layer also has a similar value of band gap with that ofbulk silicon nitrides, ~5 eV. Thus, it is an interesting issue tostudy the band gap and band offset in the hetero-double-layer
structure.
References[1] W. J. Choyke, H. Matsunami, and G. Pensl, Silicon Carbide Recent
Major Advances (Springer, Germany, 2004).
[2] T. Shirasawa, K. Hayashi, S. Mizuno, S. Tanaka, K. Nakatsuji, F.
Komori, and H. Tochihara, Phys. Rev. Lett. 98, 136105 (2007).
Authors

T. Shirasawaa, K. Nakatsuji, F. Komori, and H. Tochiharaa
aDept. Mol. & Mat. Sci., Kyushu University

Spin Pumping effect inSuperfluid 3He A1 phase
H. Kojima and H. Ishimoto

Fig. 2. (a) filled- and (b) Empty-state STM images of the SiON film
taken at sample bias voltages of (a) -5.0 and (b) 4.5 V. Transparent
circles indicate the bright protrusions. Ball and stick model of thesilicate layer of the SiON is overlaid, where white and red spheres are
Si and O atoms, respectively. (c) A typical I-V characteristic in STS
measurement on the SiON film.

silicon oxynitride (SiON) epitaxial ultrathin film on a 6HSiC(0001) surface [2]. Its atomic structure determined bymeans of a dynamical low-energy electron diffraction(LEED) analysis is shown in Fig. 1. The SiON film has ahetero-double-layer structure: a silicon dioxide monolayer ona silicon nitride monolayer via Si-O-Si bridge bonds. The
SiON film is grown on the unreconstructed SiC(0001)
surface with the atomically abrupt interface. Furthermore,since each O and N atom binds to two and three Si atoms
respectively, and all Si atoms are four-coordinated, there are
no dangling bonds in the unit cell. Actually, the SiON film isvery stable even in air!
High-resolution scanning tunneling microscopy (STM)
and spectroscopy (STS) have been successfully applied tothe insulating SiON ultrathin film [2]. Atom-resolved filledand empty-state STM images of the same area support theatomic arrangement of the silicon dioxide layer of the SiON
in Fig. 2(a) and (b), respectively, where ball and stick modelof the silicon dioxide layer is overlaid and protrusions in theimages are outlined by transparent circles for clarification. It
is clearly seen that the bright protrusions are positioned at
different sites between filled- and empty-state images. In
bulk SiO2 and Si2N2O, density of states (DOS) of the
conduction band is mostly originated from Si orbitals, andnear the valence band maximum O 2p orbitals have prominent DOS. Thus, we can conclude that the protrusions in thefilled- and empty-state images correspond to O and Si atoms,
respectively. It is surprising that STS I-V characteristic
measured on the silicon dioxide layer in Fig. 2(c) shows

When liquid 3He is cooled down to low enough temperatures in a magnetic field, the normal liquid first makes atransition into superfluid A1 phase at Tc1 and then into superfluid A2 phase at a lower temperature Tc2. The most important aspect of the A1 phase is that its superfluid component is
totally spin-polarized along the magnetic field. It is a kind offerromagnetic superfluid. A mass superflow is then simultaneously a spin flow. The phase transition into the A1 phase isaccompanied by the spontaneous breaking of relative spingauge symmetry. Interesting hydrodynamic effects occur in
the A1 phase such as a unique magnetic fountain pressure
effect which was predicted by Liu [1] and established by
Kojima [2]. Our recent experiments on this interesting
magnetically driven superflow show a peculiar spin relaxation that is dependent on temperature and magnetic fields[3]. The results can be interpreted in terms of intrinsic spin
relaxation based on Leggett and Takagi theory[4] and thepredicted presence of small but increasing presence ofminority spin pair condensate in A1 phase [5].
In these measurements, we recognized a spin pumping
effect and found a new method to derive the spin relaxation
time in the A1 phase. A sample cell has a large reservoir thatis connected to a small detector chamber through a superleak made of two channels of width 20 µm. A flexible Myler

Fig. 1. Membrane's displacement corresponding to the pressure change
in the A1 phase at 29 bars and 8T.

ISSP Activity Report 2006

43

Fig. 2. Nominal spin relaxation time derived from mechanical andmagnetic effects at 29 bars and 8T as a function of reduced temperature.

membrane dividing the two chambers forms a capacitancewith a fixed electrode. It works as a very sensitive differential pressure sensor and also as a pump to produce a polarized spin flow into the detector chamber. A pulsed large DC
voltage (about 30 V) on the capacitance sensor induces asimultaneous mass and spin superfluid flow into the smallchamber (spin pump). After thermal equilibration, release of
the DC voltage causes a sudden pressure drop followed by aslow relaxation (Fig.1). The sudden drop (∆P) is a consequence of reversed superfluid flow through the superleak. It
is compensated by the produced spin density difference (∆S).
The observed decay times during the slow relaxation are
shown in Fig 2. They are in good agreement with the spin
relaxation times obtained in the magnetic fountain effect.
These observations support our interpretation that theobserved slow relaxation stems from spin relaxation.
References[1] M. Liu, Phys. Rev. Lett. 43, 1740 (1979).
[2] R. Ruel and H. Kojima, Phys. Rev. B 28, 6582 (1983).
[3] A. Yamaguchi, S. Kobayashi, H. Ishimoto, and H. Kojima, Nature
444, 909 (2006).
[4] A. J. Leggett and S. Takagi, Ann. Phys. 106, 79 (1977).
[5] H. Monien and L. Tewordt, J. Low Temp. Phys. 60, 323 (1985).
Authors
A. Yamaguchi, S. Kobayashi, H. Ishimoto, and H. Kojimaa

aSerin Physics laboratory, Rutgers University

Fig. 1. Dependence of interlayer conductivity of Q1D conductors onmagnetic field orientations. The distance and the direction from theorigin indicate the logarithm of interlayer conductivity and the fieldorientation, respectively. (a) experiment in (TMTSF)2PF6. (b) calculation using analytic formula.

stacking (c*-) axis, respectively. In the figure, the distanceand the direction from the origin indicate the logarithm ofinterlayer conductivity and the field orientation, respectively.
Fig.1(a) contains all of the angular effects known in Q1D
conductors, that is, the Lebed resonance, the Danner-KangChaikin oscillations, the third angular effect, and the LeeNaughton oscillations. Although they have been discussed
separately so far, the present results show that they areclosely related one another in intermediate field orientations.
We can see that the most fundamental effect is the Lebed
magic angle resonance which looks like fins, and othereffects result from the amplitude modulation of the Lebed
resonance.
Figure 1(b) shows the stereographic plot of interlayer
conductivity calculated for Q1D conductors based of analytic
semiclassical theory, which corresponds to the lowest ordercontribution of interlayer coupling in the quantum theory.
We can see that most of observed features are well explainedby the existing theories. However, there is a critical discrepancy between experiment and theory, that is, the appearanceof the horizontal fin in Fig.1(a). Experimentally, the interlayer conductivity shows remarkable enhancement undermagnetic fields parallel to the conducting plane (x-y plane or
crystalline a-b' plane). This is an anomalous magnetotransport behavior since the parallel field gives the Lorentz force
most effectively.
Figure 2 shows the top view of Fig.1(a). We can see thatthe edge of the horizontal fin forms almost an perfect circle

Three-Dimensional Picture of theInterlayer Magnetoresistance of QuasiOne-Dimensional Layered Conductors
W. Kang and T. Osada
We have experimentally investigated the interlayer
magnetoresistance of the representative quasi-one-dimensional (Q1D) layered organic conductor, (TMTSF)2PF6, overthe full range of magnetic field orientations in three dimensions. We have also compared the obtained experimental
results with existing semiclassical and quantum theories [1].
Figure 1(a) shows the stereographic plot of interlayer
conductivity measured in (TMTSF)2PF6. The x-axis and zaxis correspond to the crystalline 1D (a-) axis and the

44

ISSP Activity Report 2006

Fig. 2. Top view of Fig.1(a). The edge of the horizontal fin shows inplane isotropy as shown by broken circle except near the a-axis.

except near the 1D axis (crystalline a-axis). It means that thein-plane conductance enhancement depends not on the inplane field component but only on the normal field component Bz. This fact suggests that the in-plane conductanceenhancement relates to some transport nature of 2D
conducting planes.
According to the confinement theory proposed by Strong,
Clark, and Anderson [2], the in-plane magnetic field decouples the multilayer to independent 2D layers, where interlayer conductivity obeys a scaling low depending only on Bz.
Although the observed in-plane conductivity enhancement
seem to be explained by the confinement theory, further
experimental confirmation would be necessary.
References[1] W. Kang, T. Osada, Y. J. Jo, and H. Kang, Phys. Rev. Lett. 99(2007) to be published.
[2] S. P. Strong, D. G. Clarke, and P. W. Anderson, Phys. Rev. Lett.
73, 1007 (1994).
Authors
W. Kang, Y. J. Jo, H. Kang, E. Ohmichi, K. Uchida, T. Konoike, andT. Osada

Discovery of the Most Stable Metallic
Phase in Purely d-Electronic Conductors
Based on the Transition-Metal Complex
K. Otsubo, H. Kitagawa, and Y. Uwatoko
Recent years, a halogen-bridged mixed-valencebinuclear-metal complex, the so-called MMX-Chain, hasbeen attracted significant attention owing to a variety ofstructural and physical properties derived from 1-D delectron system [1]. The title complex, Pt2(dtp)4I (dtp =C2H5CS2 ) is a special case among MMX-Chain complexes,
because it exhibits high electrical conductivity (~ 5 S cm-1)
and a metal-insulator transition at 205 K at ambient pressure
indicating that its electronic states changes depending on
temperature [2]. In this study, our attention focused on thenovel electronic state of Pt2(dtp)4I in the high pressure
region, because an application of high pressure enables tocontrol various physical parameters successively, such as
electron-transfer-integral (t), lattice constant, electron-latticeinteraction (S), and so on. To clarify the electrical transport
property and electronic states of Pt2(dtp)4I under highpressure, electrical resistivity measurement was performed
using a cubic-anvil-press system. Here, we report thatPt2(dtp)4I shows the most stable metallic phase in the 1-D delectronic metal-complex-based system, and furthermore, we
demonstrate a novel pressure-induced metal-insulator transition at 3.0 GPa.
Figure 1 (a) shows the pressure dependence of theelectrical resistivity of Pt2(dtp)4I along the b axis (// 1-D
chain) at 298 K. As the pressure is increased, the electricalresistivity decreased rapidly, but a sharp transition at 3.0 GPa
and a gradual decrease up to 8.0 GPa were observed.
Temperature dependences of the electrical resistivity at 0,
2.2, 4.0, and 8.0 GPa are shown in Fig. 1 (b). At ambientpressure, the metal-insulator transition was observed at 205
K. Under 2.2 GPa, the metallic conduction was stabilized bypressure, metal-insulator transition temperature (TM-I) was
lowered down to 70 K. As is well known, the first 1-D
molecular conductor K2Pt(CN)4Br0.3⋅nH2O (KCP(Br)) had
so far held the lowest TM-I (= 210 K under 3.2 GPa) [3].

Fig. 1. (a) Pressure dependence of the electrical resistivity at 298 K. (b)Temperature dependences of the electrical resistivity under 0, 2.2, 4.0,
and 8.0 GPa.

However, our result (TM-I = 70 K) is lower by 140 K and 1-D
metallic phase of Pt2(dtp)4I is much more stabilized. Thus,
we demonstrated that Pt2(dtp)4I is the most stable metal in
1-D purely d-electronic conductors based on the transitionmetal complexes. On the other hand, the electrical transport
behavior changed to be narrow gap semiconductor in thewhole temperature region above 3.0 GPa. These results
indicate that the resistivity jump at 3.0 GPa is due to apressure-induced metal-insulator transition.
To clarify the origin of the pressure-induced metalinsulator transition, X-ray oscillation photographs were taken
under high-pressure using a diamond-anvil-cell at KEK-PF
BL-1B. Any diffuse scatterings or superlattice reflections at
k = n + 0.5 (n : integer) originating from 2-fold periodic
charge ordering, such as charge-density-wave (CDW :⋅⋅⋅⋅⋅⋅Pt2+-Pt2+⋅⋅⋅⋅⋅⋅I–Pt3+-Pt3+–I–) or alternate-charge-polarization (ACP : ⋅⋅⋅⋅⋅⋅Pt2+-Pt3+–I–Pt3+-Pt2+⋅⋅⋅⋅⋅⋅I⋅⋅⋅⋅⋅⋅) states were
not observed above 0.5 GPa at room temperature, suggestingthat the electronic state above 0.5 GPa is not CDW or ACP
but averaged-valence (AV : –Pt2.5+-Pt2.5+–I–Pt2.5+-Pt2.5+–I–)or charge-polarization (CP : ⋅⋅⋅⋅⋅⋅Pt2+-Pt3+–I⋅⋅⋅⋅⋅⋅Pt2+-Pt3+–I–)
states. Pressure dependences of the lattice constant b and unit
cell volume V at room temperature are shown in Fig. 2.
These parameters decreased monotonically with applying
pressure, but the discontinuous jump was observed at 3.0
GPa. These results indicate that the pressure-induced metal-

Fig. 2. Pressure dependences of the lattice parameter b (red) and unit
cell volume V (blue).

ISSP Activity Report 200645

insulator transition at 3.0 GPa is attributable to a first-order
structural phase transition with elongation of b-axis (// chain)
resulting in a lowering of the electron transfer integral (t) [4].
Our present results of Raman sprectra under high pressure
supported this structural phase transition at 3.0 GPa.
References[1] C. Bellito, A. Flamini, L. Gastaldi, and L. Scaramuzza, Inorg.
Chem. 22, 444 (1983).
[2] M. Mitsumi, T. Murase, H. Kishida, T. Yoshinari, Y. Ozawa, K.
Toriumi, T. Sonoyama, H. Kitagawa, and T. Mitani, J. Am. Chem.
Soc. 123, 11179 (2001).
[3] M. Thielemans, R. Deltour, D. Jerome, and R. Cooper, R. J. Solid
State Commun. 19, 21 (1976).
[4] K. Otsubo, A. Kobayashi, H. Kitagawa, M. Hedo, Y. Uwatoko, H.
Sagayama, Y. Wakabayashi, and H. Sawa, J. Am. Chem. Soc. 128,
8140 (2006).
Authors
K. Otsuboa, A. Kobayashia, H. Kitagawaa, M. Hedo, Y. Uwatoko,
H. Sagayamab, Y. Wakabayashib, and H. Sawab
aDepartment of Chemistry, Faculty of Science, Kyushu University
bPhoton Factory, Institute of Materials Structure Science, High-Energy
Accelerator Research Organization

New Ordered State in the Strongly
Correlated Oxide BaIrO3
T. Nakano and Y. Uwatoko
Discovery of a new ordered state is one of the most interesting topic in condensed matter physics. BaIrO3 is apromising candidate in which a new ordered state may berealized. The crystal structure of BaIrO3 is monoclinic with azigzag chain of Ir3O12 trimers along the c axis [1] as shownin the inset of Fig 1. Each trimer shares the corner with aneighboring trimer, and forms a corrugated honeycomb
network along the ab plane. BaIrO3 shows weak ferromagnetism with small magnetic moment of 0.04 µB/Ir below Tc =180 K [2-4] and a gap-type order characterized by a humptype resistivity [3, 4], a hum-type Seebeck coefficient [4, 5]
and a gap-like optical spectrum [6] below Tc. Fermi surface
nesting is predicted by the band calculation [7], and acharge-density-wave (CDW) state was proposed as an originof the gap-type ordered state [3]. However, direct evidence
for CDW, that is, satellite reflections or soft phonons is not
yet observed at present. To clarify the nature of the 180-K
transition, we measured the pressure dependence of the resistivity.

Fig. 1. Pressure dependence of the resistivity of a single-crystal sampleof BaIrO3 along to the c axis. Inset: Schematic crystal structure of
BaIrO3.

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ISSP Activity Report 2006

Fig. 2. Tow-dimensional color plot of dρ/dT of BaIrO3 on the temperature-pressure phase diagram.

Figure 1 displays the resistivity ρ of BaIrO3 underpressure along the c axis. At ambient pressure, the resistivity
gradually increases with decreasing temperature from 300 K
down to Tc, and shows a hump-type anomaly at Tc. Withfurther decreasing temperature, it shows a broad maximum ataround 120 K, and decreases down to 20 K with metallic
temperature dependence (dρ/dT>0). Below 20 K, the resistivity suddenly increases again. By applying pressure, theresistivity is dramatically increased, and the metallic conduction below Tc disappears above 1 GPa. This is quite unconventional pressure dependence. Tc shifts to lower temperature with increasing pressure. Pressure dependence of Tc(dTc/dP) evaluated to be –29 K/GPa is relatively large,
suggesting that the electronic states are coupled with thelattice. However, if the ground state were CDW, the normal
state above Tc should be metallic. This is seriously incompatible to the fact that pressure makes the system more insulative in spite of dTc/dP < 0.
Figure 2 displays the T-P phase diagram by using a twodimensional color plot of dρ/dT and Tc(P). The boundary
between the yellow and blue colors is clearly illustrated
below 1 GPa, and the metallic conduction is highlighted by
the red color. Above 1 GPa, the phase boundary is somewhat
smeared, and the insulating region below Tc seems to merge
with non-metal region above Tc.
Instead of the CDW scenario, we propose an alternativemodel for the 180-K transition. Let us consider the electronic
states of a Ir3O12 trimer by neglecting the inter-trimer
hopping. For the trigonally distorted IrO6 octahedron, a1g
level is half filled by 5d electrons of Ir4+. Three a1g orbitalsof each trimer would then compose the bonding(B), nonbonding(NB) and anti bonding(AB) states. When hybridization in the inter-trimer is sufficiently small, BaIrO3 can be
regarded as a half-filled system, in which one 5d electron
occupies the NB state with the other two electrons occupying
the bonding state on each trimer. Thus the insulating state
above Tc can be regarded as a Mott insulator. On the other
hand, two inequivalent trimers due to the monoclinic distortion cause a finite energy difference ∆E between the NB
states. ∆E would increase with decreasing temperature,
because the BaIrO3 shows negative thermal expansion along
the c axis(not shown). At a certain temperature, chargetransfer can occur from the higher to lower NB state when
∆E exceeds the intra-trimer Coulomb repulsion. In thiscontext, the charge-transferred state below Tc may be
regarded as a band insulator. We believe that this is theorigin of the 180-K transition of BaIrO3.
References[1] T. Siegrist and B. L. Chamberland, J. Less-Common Met. 170, 93(1991).
[2] R. Lindsay, W. Strange, B. L. Chamberland, and R. O. Moyer, Jr,
Solid State Commun. 86, 759 (1993).
[3] G. Cao, J. E. Crow, R. P. Guertin, P. F. Henning, C. C. Homes, M.
Strongin, D. N. Basov, and E. Lochner, Solid State Commun. 113, 657(2000).
[4] T. Nakano and I. Terasaki, Phys. Rev. B 73, 195106 (2006).
[5] N. S. Kini, A. Bentien, S. Ramakrishnan, and C. Geibel, Physca B
359-369, 1264 (2005).
[6] K. Maiti, R. S. Singh, V. R. R. Medicherla, S. Rayaprol, and E. V.
Sampathkumaran, Phys. Rev. Lett. 95, 016404 (2005).
[7] M. -H. Whangbo and H. -J. Koo, Solid State Commun. 118, 491(2001).
Authors
T. Nakanoa,b, I. Terasakia,b, M. Hedo, and Y. Uwatoko
aWaseda University
bCREST/JST

Physical Properties and Pressure effecton TN in SmMIn5 (M=Co, Rh, Ir)
Y. Inada and Y. Uwatoko
SmMIn5 (M = Co, Rh, Ir) crystallizes in the tetragonal
HoCoGa5-type structure. This type of crystal structure is
known as a tetragonal variant of the AuCu3 cubic crystal
structure, and in which new superconductors were discovered [1, 2]. CeMIn5 (M = Co, Rh, Ir) compounds exhibit avariety of interesting properties such as non-s-wave-superconductivity, a first-order transition near the upper criticalfield, heavy-fermion behavior, pressure-induced superconductivity, etc. [3, 4]. Recently, superconductivity in PuCoGa5and PuRhGa5 was discovered, and they are known as heavyfermion “high Tc” superconductors [2,5]. In the exotic heavy
fermion superconductors, Cooper pairs are expected formed

Fig.1. (a) Specific heat divided by temperature (C/T) and corresponding
magnetic entropy as a function of temperature for SmRhIn5, (b) C/T vs
T for SmCoIn5, and (c) static magnetic susceptibility χ of SmCoIn5.

Fig. 2. Pressure dependence of the ratio of TN to TN at 0 GPa on
SmMIn5.

by the exchange of magnetic spin fluctuations, in which felectrons are not simply localized and they play an importantrole. A large specific heat coefficient and low antiferromagnetic ordering temperatures are features of the exotic heavyfermion superconductors.
Pu has valence states of Pu3+ (5f 5), Pu4+ (5f 4), Pu5+, Pu6+
in Pu based compounds, while it is known that Sm has Sm2+
(4f 6), Sm3+ (4f 5). Sm3+ (4f 5) and Pu3+ (5f 5) ions have thesame J=5/2 multiplet, and show the local moment behavior,i.e., obey a Curie-Weiss law. It is interesting that it depends
on the particular crystal structure whether Sm compounds
show exotic behavior or not. It is interesting to compare
SmMIn5 and heavy fermion “high Tc” superconductors of
PuCoGa5 and PuRhGa5.
We have succeeded in growing single crystals of
SmMIn5 (M= Co, Rh, Ir) by the flux method [6]. The
physical properties of single crystals of SmRhIn5 and
SmIrIn5 have already been reported [7], but there was noreport on single-crystalline SmCoIn5 before our works.
Figure 1(a) shows the specific heat divided by temperature and the corresponding magnetic entropy below 30 K, for
SmRhIn5 and LaRhIn5. The non-magnetic contribution of
LaRhIn5 has been subtracted from the specific heat of
SmRhIn5 to calculate the magnetic entropy. Two clear peaks
were observed, of which the upper one corresponds to theantiferromagnetic order. The upper transition temperature TN
is 15.0 K. The lower transition temperature is 8.3 K. The
magnetic entropy is about 75% of Rln4 at TN. This is similar
to the case of SmSn3 with AuCu3 cubic crystal structure [8].
The ground-state level of SmSn3 is a Γ8 [8], however, Γ8
quartet splits into two doublets in the tetragonal crystal structure, leading to three doublets. It is probable that there are
two adjacent doublet levels in SmRhIn5. SmRhIn5 shows the
localized f electron nature.
Figure 1(b) shows the specific heat divided by temperature versus temperature for SmCoIn5 , and Fig. 1(c) the static
magnetic susceptibility measured in an applied field of 0.1 T
for the field along the c axis (triangles) and perpendicular tothe c axis (circles) below 30K. The magnetic susceptibility
shows anisotropic behavior similar to SmRhIn5. Three
anomalies are observed both in the temperature dependenceof C/T and χ. The temperatures of these anomalies are 6 K,
7.6 K and 11.9 K. The Neel temperature of 11.9 K is thelowest value found in SmMIn5 compounds. It is expectedthat SmCoIn5 is closer to the delocalized state than SmRhIn5
and SmIrIn5. However, the value of C/T at 2 K in SmCoIn5
is 53mJ/molK2 which is not a large value compared to
PuCoGa5 or PuRhGa5. Therefore, it may be concluded thatthe 4f electrons in SmCoIn5 are more localized than 5f
electrons in PuCoGa5.

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47

In order to track the pressure evolution of the value ofTN, we have measured the electrical resistivity on single
crystals of SmMIn5 using a cubic anvil pressure cell attemperature 2-300 K under high pressure from 2 to 10 GPa.
Figure 2 shows the pressure dependence of the ratio of TN tothat at ambient pressure. The TN at ambient pressure is 15.0
and 14.9 and 11.9 K for SmRhIn5, SmIrIn5 and SmCoIn5,
respectively. This result indicates there is a tendency for TN
to clearly decrease with lower TN at ambient pressure. The
extent of delocalization probably becomes larger in order of
SmCoIn5 > SmIrIn5 > SmRhIn5. The similar tendency wasobserved in CeMIn5. The d band levels in M may beconcerned with delocalization of 4f electrons. The pressure
evolution of TN above 10 GPa is interesting, especially in
SmCoIn5. What kind of state of 4f electrons will realize athigher pressure range in SmCoIn5?
References[1] J. D. Thompson et al., J. Magn. Magn. Mater. 226, 5 (2001).
[2] J. L. Sarrao et al., Nature 420, 297 (2002).
[3] A. Bianchi et al., Phys. Rev. Lett. 91, 187004 (2003).
[4] H. Hegger et al., Phys. Rev. Lett. 84, 4986 (2000).
[5] F. Wastin et al., J. Phys. Condens. Matter 15, S2279 (2003) .
[6] Y. Inada et al., Physica B 378-380, 421 (2006).
[7] P. G. Pagliuso et al., Phys. Rev. B 63, 054426 (2001).
[8] M. Kasaya et al., J. Magn. Magn. Mater. 52, 289 (1985).
Authors
Y. Inadaa, T. Sadamasaa, M. Koeda, M. Hedo, T. Fujiwara, andY. Uwatoko
aDepartment of Science Education, Faculty of Education, Okayama
University

New Models of Polymer
Crystallization under Shear:
Shish-Kebab Structure Revisited
Shibayama GroupIn the rich and long-standing literature on the flowinduced formation of oriented precursors to polymer crystallization, it is often asserted that the longest, most extended
chains are the dominant molecular species in the “shish” of
the “shish-kebab” formation [1]. We performed a criticalexamination of this widely held view, using deuterium
labeling to distinguish different chain lengths within an
overall distribution. Small-angle neutron-scattering (SANS)
patterns of the differently labeled materials showed that long
chains are not overrepresented in the shish relative to theirconcentration in the material as a whole. We observed thatthe longest chains play a catalytic role, recruiting otherchains adjacent to them into formation of the shish.
Three model isotactic polypropylene (iPP) resins withwell-matched overall molar mass distributions-but different
chain lengths labeled with deuterium-were prepared byblending hydrogenated and deuterated polymers. These threemodel resins contained labeled chains of 13 wt% in the
shortest third (Mw = 41 kg/mol), the middle third (Mw = 197
kg/mol), or the longest third (Mw = 1781 kg/mol) of theoverall distribution, denoted Short-D, Medium-D, and LongD, respectively. Here, Mw is the molecular weight of thelabeled iPPs. Each of the deuterium-labeled resins was
subjected to identical flow at 180°C and thermal history toform specimens that had a skin-core morphology. The
transient response during and after flow, as well as final
morphology, was consistent for the three samples. During the

Fig. 1. SANS patterns of iPPs blended with Low-D, Medium-D, andHigh-D, and a model of shish-kebab structure showing the relationship.

shear pulse, all three materials showed similar birefringence
traces, characteristic of formation of oriented precursors.
Very different SANS patterns were observed as afunction of the length of the labeled chains (Fig. 1) [2].
Parent lamellar stacks were clearly evident in all threesamples as the lobes of intensity in the meridional direction;strong equatorial scattering was evident near the beamstop.
The sample containing deuterated short chains exhibitedmuch stronger scattering than those with labeled medium orlong chains. In Short-D, the deuterium label became concentrated in the lamellar crystallites. Because their coil dimensions are smaller than the long spacing, the short chainsrarely form tie chains between neighboring lamellae, so few
of their segments become trapped in the interlamellar region.
Thus, the short chains abandon the interlamellar region, but
medium and long chains are trapped there, both because theycannot add to the growth front as quickly as it passes by andbecause they are more likely to be frustrated by attaching tomultiple stacked lamellae. Therefore, the scattering from thelamellar stacks in Medium-D and Long-D is much weaker
and arises from a relative excess of deuterium in the noncrystalline interlamellar material. The elevated orientation
created near the shish causes rapid ordering. Direct measurement of chains of different lengths partitioning into the shish
shows that the fraction of long-chain segments within theshish matches their composition in the melt as a whole. This
indicates that the long chains recruit neighboring chains tojoin them in forming the shish (Fig. 2) [2, 3].
References[1] Z. Bashir, J. A. Odell, and A. Keller, J. Mater. Sci. 21, 3993 (1986).
[2] S. Kimata, T. Sakurai, Y. Nozue, T. Kasahara, N. Yamaguchi, T.
Karino, M. Shibayama, and J. A. Kornfield, Science 316, 1014 (2007).
[3] M. Seki, D. W. Thurman, J. P. Oberhauser, and J. A. Kornfield,
Macromolecules 35, 2583 (2002).

Fig. 2. Mechanism of shish-kebab formation.

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ISSP Activity Report 2006

Authors
S. Kimataa,b, T. Sakuraia, Y. Nozuea, T. Kasaharaa, N. Yamaguchia, T.
Karino, M. Shibayama, and J. A. Kornfieldb
aPetrochemicals Research Laboratory, Sumitomo ChemicalbDivision of Chemistry and Chemical Engineering, California Instituteof Technology

Epitaxial A-site Ordered Perovskite
Manganite SmBaMn2O6 Thin Filmon SrTiO3(001)
T. Nakajima and Y. Ueda
Perovskite manganites have been intensively studied
about their huge MR effect, the so-called colossal magnetoresistance (CMR) effect. In perovskite manganite thinfilms that show the CMR effect, the light-induced insulatormetal transition has also been realized in the CMR manganites by Takubo et al. [1]. Because of these properties, theperovskite manganites show promise for applications such as
electronic switching devices that use a magnetically or
optically induced phase change. However, CMR manganites
such as La1-xCaxMnO3 have a disadvantage for the application: namely, the CMR is observed far below room temperature. Therefore, the development of new materials thatexhibit CMR near room temperature is desirable. Recently,
we synthesized A-site ordered manganites RBaMn2O6, anddiscovered that La-doped SmBaMn2O6 exhibits 1000%
CMR under 9 T at 300 K [2]. However, the thin films of Asite ordered perovskite manganites have not been prepared so
far by conventional film-forming methods, while the fabrication of films is essential for the practical applications.
Therefore, we have investigated the fabrication of A-siteordered manganite thin films using a new process, anexcimer laser assisted metal organic deposition (ELAMOD)
process. An A-site ordered perovskite manganite
SmBaMn2O6-δ (δ ≅ 0.5) film was fabricated by means of the
ELAMOD, and epitaxially grown on a SrTiO3(001)substrate. The SmBaMn2O6-δ film was crystallized in [010]and [001]-oriented domains that were confirmed by X-ray
diffraction and cross-section transmittance electron
microscopy (TEM) as shown in Fig. 1. The A-site orderedstructure formed at 500 °C under KrF laser irradiation at alaser fluence of 140 mJ/cm2 for 60 min in an Ar flow,whereas disordered A-site cations formed under laser irradiation at fluences less than 120 mJ/cm2 and/or in an oxygenFig. 1. Cross-sectional TEM image of the SmBaMn2O6 film on
SrTiO3(001).

atmosphere. A SmBaMn2O6 film was obtained by oxygenannealing of the as-prepared SmBaMn2O6-δ film at 500 °C
for 3 h. The electrical resistivity for the SmBaMn2O6 film on
SrTiO3(001) show insulating behavior without a first-ordercharge/orbital order (CO) transition caused by constraint oflattice change associated with the CO due to theundeformable substrate lattice. The ELAMOD process is
expected to serve as a new key technique for the fabricationof A-site ordered perovskite manganite thin films.
References[1] N. Takubo, Y. Ogimoto, M. Nakamura, H. Tamaru, M. Izumi, andK. Miyano, Phys. Rev. Lett. 95 017404 (2005).
[2] T. Nakajima and Y. Ueda, J. Appl. Phys. 98 046108 (2005).
Authors
T. Nakajimaa, T. Tsuchiyaa, M. Ichihara, Y. Ueda, and T. Kumagaia
aNational Institute of Advanced Industrial Science and Technology

Electronic Structure of β-FeSi2
H. Udono, K. Takarabe, and H. Tajima
Semiconducting iron disilicide, β-FeSi2, is increasingly
attracting attention as a suitable material for use in Si-based
optoelectronics, because β-FeSi2 has a band gap in the nearinfrared (NIR) region and a very high refractive index (5-6),
and its film is epitaxially grown on Si substrate using a
conventional Si-ULSI process. Recent reports on the 1.56 1.6 µm light emitting diodes and high index-contrast
photonic crystal devices using β-FeSi2/Si have dramatically
remotivated the interest in β-FeSi2 [1]. However, theluminescence mechanism and the electronic structure havenot been clarified, yet. The band gap nature of bulk β-FeSi2
is indirect and its gap energy is expected to be around 0.7eV
at 300K [2, 3]. Thus, we have investigated the electronic
structure using the band calculation based on the first-principles method and polarized optical reflection (PR) measurements on single crystalline β-FeSi2.
The calculated band structure is shown in Fig. 1(a). Theband structure of β-FeSi2 was characterized by an indirecttransition of 0.67eV between the valence band maximum(VBM) at the Y point and the conduction band minimum

Fig. 1. (a) Band structure of β-FeSi2 along high symmetry axes. The
valence-band maximum at the Y point is taken as the reference energy.
PR spectrums of β-FeSi2 single crystal for (b) E//a, (c) E//b, and (d)E//c light polarization. The solid lines are the theoretical spectrums.

ISSP Activity Report 200649

References[1] T. Suemasu et al., Jpn. J. Appl. Phys. 39 L1013 (2000).
[2] H. Udono, I. Kikuma, T. Okuno, Y. Masumoto, and H. Tajima,Appl. Phys. Lett. 85, 1937 (2004).
[3] H. Udono, I. Kikuma, T. Okuno, Y. Masumoto, H. Tajima, and S.
Komuro, Thin Solid Films 461, 182 (2004).
[4] H. Udono, I. Kikuma, H. Tajima, and K. Takarabe, J. Mater. Sci.,
DOI 10.1007/s10854-007-9166-z (2007).
Authors
H. Udonoa K. Takarabeb and H. Tajima
aCollege of Engineering, Ibaraki University
bOkayama University of Science

Giant Intrinsic Spin Hall Effect inTransition Metal Complexes[Sr2RuO4, Platinum]
Fig. 2. Imaginary parts (ε2) of the dielectric function of β-FeSi2 single
crystal for (a) E//a, (b) E//b, and (c) E//c light polarization. The solidlines are the theoretical spectrums. A-L and a-l denote the peaks orshoulders in the experimental and theoretical spectrum, respectively.

(CBM) situated along the G-Z (L) direction. The first directtransition gap was 0.73eV at the Y point. The next direct
band gap was 0.81eV at L point. Figure 1(b)-1(d) show acomparison of the PR spectrums for the experimental andtheoretical results. The PR spectrums for E//a, E//b and E//c
reveal that the anisotropy of the reflectance depending on thelight polarization. Features of each experimental spectrum
are comparable to the theoretical calculations [4].
Figure 2 shows a comparison of the imaginary part of thedielectric function, ε2, for the experimental and theoretical
data. The spectrums for E//a, E//b and E//c had characteristically four peaks or shoulders in each spectrum as denoted AL for experimental and a-l for theoretical data, respectively.
When the theoretical spectrums are shifted 0.8- 0.14 eV tothe lower energy, the transition energies at the peaks orshoulders in the experimental spectrums corresponds well tothose in the theoretical ones, e.g., A-D, E-H and I-L correspond to a-d, e-h and i-l, respectively. Furthermore, relative
intensity of each peak or shoulder in both experimental andtheoretical spectrums (A-L and a-l) agreed well in eachother. These analyses of the spectrums indicate that theenergy dependence of the dielectric function up to 3.1eV iswell reproduced by the theoretical calculation using the
FLAPW method based on the DFT and the dipole approximation.
We found that the optical properties (absorption and PR
spectrum) of bulk β-FeSi2 are well explained by the bandcalculation based on the first-principles method. However,there remain some unsolved problems. The value of direct
gap energy at Y-Y in the electronic structure is under
estimated about 0.21eV compared to the absorption experiments [3]. On the other hand, analysis of the PR spectrums
suggests the over estimation of the calculated transitionenergy for the higher interband transitions. If we assumed
that the temperature shift of the PR spectrum is about 0.04eV
at 0K as observed in the absorption spectrum, the offset
energy of about +0.1eV is derived. This value is not negligible compared to the experimental uncertainty. Therefore,
the shift of the theoretical peak position to the higher energy
as compared to the experimental one could suggest that some
additional effects should be taken into account the theoretical
calculation.

H. Kontani, D. S. Hirashima, and J. Inoue
Recently, spin Hall effect (SHE) attracts great attention
due to its fundamental interest and its potential application in
spintronics. In 1954, Karplus and Luttinger showed that anelectric field induces a spin-dependent transverse current in
the presence of spin-orbit (SO) interaction. This mechanism
causes the anomalous Hall effect in ferromagnetic metals,
and the SHE in paramagnetic metals. Recent experiment [1]revealed that the spin Hall conductivity (SHC) obtained by anon-local measurement for Pt is 104 times larger than that insemiconductors. This fact devoted considerable attention to
the SHE in transition metals.
To elucidate the origin of huge SHE in Pt, we focused
attention to the significance of d-orbital degrees of freedom,and studied the SHC in several multiorbital tight-binding
models [2, 3, 4]: Figure 1 shows a two-dimensional (dxz,dyz)-orbital tight-binding model [2], which is a simplified
model for Sr2RuO4 [3]. Here, ±t' represents the interorbital
hopping integral between next nearest sites. Now, let us
consider the motion of a down-spin electron along a triangleof half unit cell: An electron in the dxz-orbital can transfer todyz-orbital and vise versa using the z-component of SO interaction − λlz /2 where 〈 xy | lz | yz 〉 = −〈 yz | lz | xz 〉 = i. By
combination of angular dependence of interorbital hopping
and the SO interaction, a clockwise (anti-clockwise) motion
along any triangle path with SO interaction causes the factor+i (-i). This factor can be interpreted as the Aharonov-Bohm
phase factor exp(2πi φ / φ 0) [φ 0 = hc/|e|], where φ = ±φ0/4
represents the “effective magnetic flux” in the half unit cell.
We revealed that the effective magnetic flux, which isinherent in multiorbital d-electron systems, causes huge SHE
in various transition metals [2, 3, 4].

Fig. 1. Effective magnetic flux for down-electron in a (dxz,dyz)-orbitaltight-binding model.

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ISSP Activity Report 2006

Fig. 2 .(a)λ-dependence of the SHC in Pt. γ represents the quasiparticle
damping rate. (b) SHC as a function of resistivity ρ (∝ γ ).

Here, we calculate the SHC based on the linear-responseztheory: Figure 2 (a) shows the SHC (σxy ) in a (6s,6p,5d)tight-binding model for Pt [3], as a function of the SO interaction λ. The value of λ for 5d-electrton in Pt is expected to
0.03 Ry. In this case SHC exceeds 1000 /eΩcm, which isfour times large that the experimental value in Pt at room
temperature [1]. To clarify the origin of SHE in Pt, we study
the SHC when the SO interaction is anisotropic: Whereas
SHC for the XY-like SO interaction λ(lxsx + lysy) is verysmall, SHC for the Ising-like SO interaction λlzsz is as large
as that in the isotropic case. Especially, matrix elements of
λlzsz between (dxy, dx2-y2)-orbitals, both of which arecomposed of lz = ±2 gives the dominant contribution
to the SHC. Figure 2 (b) shows that the SHC is constantfor ρ <<30 µΩcm, whereas it decreases quickly forρ >> 30 µΩcm. This coherent-incoherent crossover behaviorof the intrinsic SHC also appears in the anomalous Hall
effect [2].
The present study strongly suggests that giant SHE due tothe mechanism of “effective magnetic flux” is not restricted
to Sr2RuO4 and platinum, but is ubiquitous in various p-, d-,f-electron systems with atomic orbital degrees of freedom.
References[1] T. Kimura, Y. Otani, T. Sato, S. Takahashi, and S. Maekawa, Phys.
Rev. Lett. 98, 156601 (2007).
[2] H. Kontani, T. Tanaka, and K. Yamada, Phys. Rev. B 75, 184416(2007).
[3] H. Kontani, T. Tanaka, D. S. Hirashima, K. Yamada, and J. Inoue,
cond-mat/ 0702447.
[4] H. Kontani, M. Naito, D. S. Hirashima, K. Yamada, and J. Inoue,
arXiv:0705.3535.
Authors
H. Kontania, T. Tanakaa, M. Naotioa, D. S. Hirashimaa, K. Yamadab,and J. Inouec
aDepartment of Physics, Nagoya University
bRitsumeikan University
cDepartment of Applied Physics, Nagoya University(J1), and the abundance of experimental examples. On theother hand, frustration in square-based models that involve
addition of 2NN (J2) interactions is difficult to be realized
because nature favors the dominance of the interactions for
shorter bonds, resulting in the well-known (π, π) Néelordered state.
Double-layered perovskites (CuX)LaNb2O7 (X = Cl, Br),in which Cu2+ spins forms the S = 1/2 square lattice, havebeen found to show intriguing phenomena related to geometrical frustration. (CuBr)LaNb2O7 establishes a (π, 0)collinear AF order (CAF) at 32 K with a reduced moment ~0.6 µB, while (CuCl)LaNb2O7 has the spin-singlet groundstate, with a gap of 2.3 meV in the spin excitation spectrum[1, 2]. (CuX)LaNb2O7 belongs to the Dion-Jacobson series
expressed as (CuX)An-1BnO3n+1, where A is La3+, Ca2+,
Na+ ..., B is Nb5+, Ta5+, Ti4+, n = 2, 3, 4.... The rich diversityof the family brings a crucial advantage over existing
compounds, that is, a systematic control of the magnetic
properties by varying parameters A, B, X and n. Particularlyinteresting is tuning n, by which one can control the twodimensionality (2D).
Here, we newly synthesized a triple-layered perovskite(CuBr)Sr2Nb3O10 from the ion-exchange reaction expressed
as “RbSr2Nb3O10 + CuBr2 → (CuBr)Sr2Nb3O10 + RbBr”
and measured magnetic properties [3]. Figure 1 shows thepulsed-field magnetizations divided by the saturated magnetization M(H)/Ms. The most prominent aspect is the appearance of a plateau corresponding to the 1/3 of the full magnetization, which was not found in the double-layered system.
The plateau becomes obscured with increasing T andvanishes at 9 K. The 1/3 magnetization plateau has beentheoretically predicted for various triangle-based lattices, as
experimentally verified by, e.g., Cs2CuBr4 and a copper
complex. However, for commensurability reasons calculations of the square lattice predict plateaus such as 1/2 and1/4. The present study thus calls for further attention to thefrustrated square-lattice system.
References[1] H. Kageyama, T. Kitano, N. Oba, M. Nishi, S. Nagai, K. Hirota,
L. Viciu, J. B. Wiley, J. Yasuda, Y. Baba, Y. Ajiro, and K. Yoshimura,
J. Phys. Soc. Jpn. 74 1702 (2005).
[2] N. Oba, H. Kageyama, T. Kitano, J. Yasuda, Y. Baba, M. Nishi,
K. Hirota, Y. Narumi, M. Hagiwara, K. Kindo, T. Saito, Y. Ajiro, andK. Yoshimura, J. Phys. Soc. Jpn. 75 11360 (2006).
[3] Y. Tsujimoto, Y. Baba, N. Oba, H. Kageyama, T. Fukui,
Y. Narumi, K. Kindo, T. Saito, M. Takano, Y. Ajiro, andK. Yoshimura, J. Phys. Soc. Jpn. in press.
Authors
H. Kageyamaa, Y. Tsujimotoa, Y. Ajiroa, K. Yoshimuraa, T. Fukui,
Y. Narumi, and K. Kindo
aGraduate School of Science, Kyoto University

1/3 Magnetization Plateau in S = 1/2
Quasi-Two-Dimensional
Antiferromagnet (CuBr)Sr2Nb3O10
H. Kageyama and K. Kindo
Historically, the study of geometrically frustration in spin
systems has been centered on the triangle-based models suchas triangular, kagomé and pyrochlore lattices. This is because
they simply consist of single elements of NN interactions

Fig. 1. Magnetization curves of single-crystal (CuBr)Sr2Nb3O10. The
inset shows the crystal structure (CuBr)Sr2Nb3O10, in which themagnetic (CuBr)+ layers constructing S = 1/2 square lattice are
separated by the nonmagnetic [Sr2Nb3O10]- perovskite slabs.

ISSP Activity Report 200651

International Conferences and Workshops

10th ISSP International Symposium on Nanoscience at Surfaces
October 9-13, 2006
F. Komori
Research activities in nanoscience at surfaces have been significantly growing and taking advantages of accumulated
knowledge of surface science. Previously, chemists in this field studied it as the useful ground of material formation, and physicists mainly progressed on the basis of the solid-state electron theory. Now the boundary between them should be broken down,
and this interdisciplinary field is developing beyond the frame of each other's such as in the basic science of molecular conduction and atom/molecule manipulation. At the symposium, these were indeed two of the main topics.
This symposium was the tenth in a series of international symposia organized by ISSP every two or three years, and was coorganized as the University of Tokyo International Symposium 2006. A total of 242 scientific delegates from 14 different
countries attended the symposium, and 210 papers were presented (19 invited and 21 oral contributions, and 170 posters). The
symposium provided researchers in this field the opportunity to discuss properties of nanostructures on surfaces and their fabrication processes. Various advanced approaches were introduced for quantitative observations and elucidating the origins of
newly discovered phenomena. The proceedings of the symposium is published as a special issue of Surface Science journal
from Elsevier.

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ISSP Activity Report 2006

ISSP International Workshop and Symposium"Computational Approaches to Quantum Critical Phenomena (CQCP)"
July 17 - August 11, 2006
N. Kawashima, T. Kato, Y. Tomita, S. Todo, and K. HaradaThis is the first event of what the theoretical division at ISSP intends to be a series of small international meetings oncondensed matter physics. While the main sponsor is ISSP, the symposium is also supported by I2CAM, an international organization that ISSP joined in 2005. The main objectives of the event were to survey the recent developments in computational
physics and its applications to strongly correlated quantum systems, and to initiate discussions and new collaborations in thesefields. In particular, we focused on the quantum critical phenomena, which have become tractable by various powerful numerical
techniques developed in the last decade. The last three days (August 9-11) were dedicated to the symposium whereas the rest isfor the workshop. Most of the participants stayed at campus during the workshop/symposium and intensive communications
were developed among the participants. We invited 8 speakers from abroad and another 8 from Japan. During the workshop we
had one or two lectures everyday. Typically there were 30 audiences present at the lectures. During the symposium, we had
about 80 participants. The emphasis of the workshop was on the recent progress in algorithms, techniques and methods ofcomputational condensed-matter physics. We also asked every invited speaker to make their lectures pedagogical so that
graduate students can get sufficient information to start developing basic skills in this field. Topics covered include world-line
quantum Monte Carlo, quantum Monte Carlo with dimer basis, density matrix renormalization group, exact diagonalization,
dynamical mean-field theory, and new negative-sign free Monte Carlo method based on Gaussian basis. On the other hand, thesymposium focused on new physics obtained from recent numerical calculations. We had 36 oral presentations and 19 poster
presentations including not only computational works but also experimental and theoretical works. To name some of the mostnotable discussions, we had several impressive talks on (1) deconfinement critical phenomena, (2) supersolid, (3) ordering withmagnetic quadrupoles or higher multipoles, and (4) field-induced magnetization and dimension reduction.

Taiwan-Japan Workshop on Neutron Scattering of Biomaterials and Soft-Matters
for Nanotechnology and Biotechnology
December 7-9, 2006
M. Shibayama
The first Taiwan-Japan Workshop on Neutron Scattering was held in Tokai during the period of Dec. 7 -9, 2006. In Taiwan,
synchrotron X-rays are available for scattering studies. Besides X-rays, neutrons are very essential and irreplaceable probes forstructural investigation of biomaterials and soft-matters. Japan is the most advanced country in neutron scattering in Asia and is
now developing the next generation spallation neutron source, J-PARC, and neutron scattering instruments. In order toencourage future developments of neutron scattering facilities/researches in Taiwan, it was desired to develop more close
research collaboration in applying the neutron scattering to these research fields. The objective of the meeting was to share thesuccessful experience in applying the neutron scattering in Japan to study these interdisciplinary fields with Taiwan scientists
for future neutron scattering researches of both countries. The research topics included nanomaterials, biomaterials (membrane,
protein, peptides), and macromolecules (polymers). 44 Japanese and 12 Taiwanese scientists attended the meeting, and 24 oral
and 14 poster presentations were given, covering interface, biology, polymer, soft-matter, hard-matter, and instrumentation.
The meeting was quite successful and made an agreement to have the second meeting in Taiwan in 2007. This meeting wassponsored by Interchange Association, Japan, and Thaipei Economic & Cultural Representative Office in Japan.

ISSP Activity Report 2006

53

ISSP Workshops

Electronic Properties of Nano-structured Organic Materials
April 24-26, 2006
K. Awaga, M. Yamashita, T. Matsumoto, H. Nishikawa, and H. Tajima
Electrical properties of organic materials have been studied extensively, and the research on organic semiconductors, metals
and superconductors has been well developed, based on the detailed understanding on the correlation between the
crystal/molecular structures and the bulk electrical properties. In recent years, organic semiconductors are attracting new attention as a component of organic electronic devices. This new research trend stimulates interdisciplinary studies of solid-statephysics and chemistry, surface science, applied physics, etc., and is located on a crossing point between fundamental studies
and applications. The present meeting consisted of invited and contributed talks and posters. We discussed various topics, suchas organic thin films and their device applications, various electrical properties of nano-materials and biological materials.

New Progress of Studies on Phonons Responsible for Novel Properties
June 5-7, 2006
K. Iwasa, K. Hirota, O. Yamamuro, and I. Tsukushi
Studies of structural dynamics have recently been extended to biological systems, unconventional superconductors, disordered materials, as well as dielectric systems. These are strongly supported by rapid progress of experimental techniques investigating the atomic motions; inelastic x-ray scattering, terahertz time-domain spectroscopy, light scattering, nuclear resonance,neutron scattering, and so on. The various scientific topics, techniques and theoretical arguments to reveal the dynamical
properties of material were gathered in this workshop that was held at the ISSP Kashiwa campus on June 5 - 7. The participantsfrom the aforementioned different research fields exchanged information on the current research topics and discussed the future
direction of phonon studies. We hope that this workshop will trigger interdiscipline of phonon science.

Water, Ice and Hydrogen: Earth and Space Sciences Meet Physics
October 24-25, 2006
H. Kagi, O. Yamamuro, T. Yagi, K. Aoki, E. Ohtani, T. Irifune, and K. Kakurai
The workshop attracted approximately 65 people to the ISSP Tokai campus on the basis of high-pressure science, earth andspace science, solid state physics to discuss the properties of hydrogen-bearing materials at extreme conditions. It is worthwhile
to note that many of participants are postdocs, graduate students and undergraduates. This implies that our science will further
continue to expand in near future. It is obvious to use neutron as a probe to study hydrogen in materials. We learned that manyefforts have to be made to develop new science in this field. Most of the participants also joined laboratory tours to J-PARC
and JRR-3.

Fig. 1. Discussion at the workshop

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ISSP Activity Report 2006

Fig. 2. Laboratory tour at J-PARC

Unifying Concepts of Glass Transition—Interconnections of Theories and Assessment by Experiments—
November 20-22, 2006
T. Odagaki, M. Kataoka, T. Kanaya, H. Kawamura, M. Sasai, S. Shin,T. Suzuki, H. Takayama, K. Fukao, S. Fujikawa, J. Matsui, and O. Yamamuro
Glass transition is one of the most important unsolved problems of condensed matter physics. Since mid 1980's, understanding of glass transitions has progressed significantly due to advancement in experimental techniques and invention of themode coupling theory (MCT), and now the research of glass transitions seems to have entered into a new stage. In fact, many
international conferences and/or workshops have organized since 2000; to list a few, for example, International Discussion
Meeting on Relaxations in Complex Systems (IDMRCS) in 2001 (Crete) and in 2005 (Lille), Workshop on Non Equilibrium
Phenomena in Super-cooled Fluids, Glasses and Amorphous Materials (WNEP) in 2002 and 2006 (Pisa) and Unifying
Concepts in Glass Physics (UCGP) in 2002 (Rome) and in 2004 (Bangalore). In these meetings, more and more emphasis has
been put on the landscape picture than on the MCT.
In these moves in the world community, we have organized ISSP workshop in 2002 "New developments in glass physics"
and in 2004 "Condensed matter in extremely non-equilibrium condition and energy landscape" in the Institute of Solid State
Physics, The University of Tokyo, inviting active researchers in Japan.
In order to share new developments and advancements in the world in the community, we organized ISSP workshop"Unifying Concepts of Glass Transition". The scope of the workshop reads as:
The main aim of this workshop is to give an opportunity for the participants to share new developments both intheory and experiment, by analyzing the current status of the research of glass transition in the world. We will makeclear interrelations among theories such as the energy landscape and the MCT, and assess the plausibility of experimental tests of the theories. This will clarify what should be solved in theory and in experiment on the basis of thecurrent understandings, which can be shared by all participants.
In the workshop, we had 158 participants from all over Japan (52 on 20th, 67 on 21st and 39 on 22nd), and 31 oral presentations and 13 poster presentations. From these beautiful presentations, we have learned that both theory and experiment on glasstransitions have been progressing strongly. We also had very active discussions during the sessions and at the coffee breaks,
and the workshop was successfully concluded with many outcomes formulating new themes and experiments.

Physics on Quantum Spin Systems
November 27-29, 2006
T. Sakai, H. Takayama, M. Takigawa, M. Oshikawa, H. Tanaka, and H. Kageyama
This workshop was held to search some new research fields on the quantum spin systems, and to activate comunication
among different generations. It consisted of about 30 invited, 20 contirbuted oral presentations and 40 poster presentations. We
focused on several hot topics; the nano magnets, chiral magnets, frustrated systems, spin liquids, Bose-Einstein condensation ofmagnons and Haldane systems etc. The discussions by young people after each talk were encouraged very much. As a result,more than 100 people participated the workshop every day and we had a lot ot fruitful discussions. We hope some young
participants will hold a next interesting workshop in the near future.

For Establishment of a New Research Regime of the Condensed Matter Physics
in Japan
December 7-8, 2006
M. Sato, Y. Kuramoto, Y. Murakami, Y. Suzumura, J. Akimitsu, Z. Hiroi, and H. Takayama
The proposal of the workshop was made by the chairman of the an unofficial research group of solid state physics in Japan
to discuss various subjects brought about by rapid changes of research conditions or environments of universities and otherresearch institutes after the introduction of the agency system to the universities and institutes. The introduction of a new
system to the Science Council of Japan also seemed to give much influence on the research conditions. Many researchers
actively working in the condensed matter physics participated in the workshop and constructive discussion was made on thesubjects describe below.
(1) Roles and future planning of cooperative research institutes in Japan,(2) Toward proper financial support for various researches in the condensed matter physics,(3) Functions of the new Science Council of Japan and requests of the research group to the Council,(4) To make the Japan Physical Society Meeting more effective,(5) To raise the prestige of J. Physical Society of Japan,(6) To support small-scale research groups, facing to difficulties induced by the new system,and(7) problems of the present post-doctoral system.

ISSP Activity Report 200655

Supercomputer Utilization in the Computational Condensed Matter Science— Present and Future
December 11-13, 2006
O. Sugino, H. Takayama, K. Tsunetsugu, N. Kawashima, and S. Tsuneyuki
The users of the ISSP supercomputers and computational condensed matter scientists attended this meeting to present recent
research activity and discuss future prospect. Since the last meeting of four years ago, the computer power has increased bymore than a factor of ten and the computational approach has changed qualitatively. In a number of presentations, one could see
new trend and progress in the research. There were sixty attendants and thirty two oral presentations. The meeting consisted
only of oral presentations, without poster presentations and the party.
At the second day of the meeting, we held a special session regarding the future peta flops machine, which will be manufactured and served in five years from now. There we invited not only theoreticians but also experiments; we also invited anengineer who is engaged in manufacturing the peta flops machine. After the presentations and the discussions, the attendants
have learned problems concerning the coming peta flops decade. The machine will necessarily be massively parallel machinethat has narrow channels between CPUs, meaning that the computer code needs to adapt to the computational environment. The
conversion of the code is very demanding and requires us to develop system to grow up more experts. Even after the efforts,
there will remain problems on the condensed matter science that are not adapted to this computational environment.
At the end of the meeting there was request by an attendant that this kind of meeting should be regularly held.

Advances in Semiconductor Spintronics
December 14-15, 2006
S. Katsumoto and M. Tanaka
This ISSP workshop was held for exchange of most recent information on the research of spin-related physics and applications in semiconductor devices. The workshop was also announced to the community as "11th conference on Physics andApplications of Spin-related Phenomena in Semiconductors" (PASPS11).
In the workshop, "spin" can be either electron spin or nuclear spin. Actually the topics covers a wide range, e.g., spintronics
devices, material designs, spin-related theories, synthesis and characterizations of ferromagnetic semiconductors, nuclear-spin
dependent transport, quantum manipulation of spins, and so on.
Three invited talks, one special report for making of "roadmap" in semiconductor devices, 26 oral talks and 32 posters were
presented. Each session bore lively and sometimes heated discussion.
In the field of material science, several new ways to synthesize magnetic semiconductors with high transition temperatures
were reported. The most impressive was the increase in the number of presentation on the nuclear spins. It is now clear that thetransport in quantum Hall regime is strongly affected by nuclear spins under certain conditions. Thus electrical detection andmanipulation of nuclear spins are prosperous now.
The next PASPS will be held in Osaka in 2007.

Electronic Properties of Pyrochlore Oxides
February 23, 2007
H Harima, M. Takigawa, and Z. Hiroi
This workshop was organized for understanding interesting electronic properties of pyrochlore oxides recently studied
extensively. It attracted about 50 people including 11 guests from the outside of ISSP. Presentations on the superconductivity,
Fermi surface and rattling of the beta-pyrochlore osmates were given in the first half of the workshop, and in the second half,various topics on the electronic properties and metal-insulator transitions of the alpha-pyrochlore oxides were discussed.
Extensive discussions had been carried out through the workshop. It gave a wonderful opportunity to deepen and expand ourknowledge on the pyrochlore oxides.

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ISSP Activity Report 2006