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). The SRL consists of the accelerator
physics group and the solid state spectroscopy group. The
members of the accelerator group have been carrying out
research works 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 withtechnical supports and advices, but also carrying out theirown research works on advanced solid state spectroscopy.
SRL maintains an undulator called Revolver, two beamlines
and three experimental stations; BL-18A for angle-resolved
photoemission spectroscopy and undulator 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 radiationfrom the undulator. The operation time of these beamlines
are about 4000 hours and the number of users is more than
100 a year.
In 2007, two new apparatuses have been opened to theusers. They are SCIENTA SES100 energy analyser at BL-18A
and VLEED spin detector at BL19A. The new apparatuses
are utilized in angle-resolved and spin-resolved photoemission experiments with higher energy- and momentumresolutions. Recently, our VLEED system showed the best
efficiency of this kind of spin detector (see the highlight inthis volume).
The staff members of SRL, the solid state spectroscopy group, participate to the Materials Research Divisionof the Synchrotron Radiation Research Organization of
the University of Tokyo (SRRO). They play essential roles
in promoting scientific activities using SR and started toconstruct a new 25m-long undulator and beamline at theSPring-8. The beamline will be equipped with experimental
apparatuses using high brilliance synchrotron radiation insoft X-ray region. They are those for time-resolved experiments and nano-materials research 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 reactions at catalytic surfaces, etc.
The accelerator group designed and started to construct
the new 25-m undulator of the University of Tokyo at
SPring-8 in collaboration with the SPring-8 ID group. The
new undulator consists of four horizontal and four verticalfigure-8 undulator segments and seven phase shifters
between the segments and can provide not only horizontally- and vertically-polarized radiations but also circularlypolarized radiation with fast helicity switching. The four
horizontal figure-8 undulator segments were alreadyconstructed and a prototype of the electromagnetic phaseshifter was designed and fabricated. A pulsed sextupole
magnet was developed to reduce the stored beam oscillation at top-up injection and installed in the PF-ring and adigital beam position monitor system was upgraded andits performance test was successfully carried out at ISSP
and the KEK-ATF damping ring. The accelerator group alsostudied future ERL(energy recovery linac) light sourcesand developed ERL components. Exact resistive-wall wake
function of a vacuum pipe was calculated to simulate themulti-bunch beam motion due to the resistive-wall wake inan ERL. Center and end single-cell superconducting cavities
were fabricated and tested in collaboration with KEK and
JAEA and their acceleration fields of higher than 15 MV/m
were achieved. A nine-cell cavity and two ceramic windows
for the input coupler were also fabricated and will be tested.
Furthermore a fiber laser oscillator for driving an ERL
photocathode gun was developed in collaboration with AIST
and KEK.

Neutron Science Laboratory

The new undulator arrived at SPring-8

36

ISSP Activity Report 2007

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 installedat 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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 fromthe reactor core towards the guide hall located to the left.

submitted each year, and the number of visiting users under
this program 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 also available throughthe ISSP-NSL user program.
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 inrare-earth based intermetallic compounds, spin dynamics
of low dimensional dimmer systems, etc. On the other
hand, the research topics on the soft-condensed matterscience cover structural characterization of polymer blends,
micelles, amphiphilic polymers block copolymers, liquid
crystals, proteins, inorganic gels, dynamics of brushpolymers on surface, slow dynamics of surfactants, pressure
dependence of dynamics of amphiphilic membranes, andso on. In addition, there are a variety of activities on fundamental physics, neutron beam optics, developments ofneutron 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 are reported in the NSL-ISSP Activity Report vol. 14.

Supercomputer Center
The Supercomputer Center (SCC) is a part of theMaterials Design and Characterization Laboratory (MDCL) of
ISSP. Its mission is to serve the whole community of computational condensed-matter physics of Japan providing it withhigh performance computing environment. In particular, the
SCC selectively promotes and supports large-scale computations. For this purpose, the SCC invites proposals for supercomputer-aided research projects and hosts the Steering
Committee, as mentioned below, to evaluate the proposals.
The SCC 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. With theaid of the automatic parallelization of FORTRAN compiler,a node of System A can be used as if it were a singleprocessor computer. System A has 2.8TB memory andachieves 5.8 TFlops peak performance in total. On the other
hand, System B, which is SGI Altix 3700/1280, is a parallel
supercomputer with relatively loose coupling. It consists of
19 nodes inter-connected by a gigabit Ethernet network.
Each node is a distributed-shared-memory-type computerconsisting of 64 Intel Itanium 2 CPUs interconnected by arather high performance network and have 64 GB memory.
System B achieves 7.7 TFlops total throughput performance.
All staff members of university faculties or publicresearch institutes in Japan are invited to propose research
projects (called User Programs). The proposals are evaluatedby the Steering Committee of SCC. Pre-reviewing is doneby the Supercomputer Project Advisory Committee. In fiscal
year 2007 totally 184 projects were approved. The total
points applied and approved are listed in Table. 1 below.
The research projects are roughly classified into thefollowing three (together with the number of approved
projects):
First-Principles Calculation of Materials Properties (67)
Strongly Correlated Quantum Systems (49)
Cooperative Phenomena in Complex, Macroscopic
Systems (68)
All the three involve both methodology of computationand its applications. The results of the projects are reported
in 'Activity Report 2007' of the SCC. Every year typicallyfour projects are selected for invited papers, which appear
at the beggining of the Activity Report. In the Activity
Report 2007, the following four invited papers are included:“Gaussian-Basis Monte Carlo Studies on Two
Dimensional Hubbard Model”, by Takeshi AIMI, Daisuke
TAHARA and Masatoshi IMADA“First-Principles Study of Multiferroic Oxides” by Tamio
OGUCHI“Hydration Effect on Temperature Dependence of Protein
Dynamics Studied by Molecular Dynamics Simulation of
Crystalline Protein” by Yasumasa JOTI and Akio KITAO“Quantum Phase Transitions to VBS States” by Naoki
KAWASHIMA and Kenji HARADAClass Max/Min
PointsApplication

Numberof
Projects

Total Points
AppliedApproved

System A

System B

System A

System B

A<100K

any time

8

470K

330K

470K

330K

B

<2M

twice a year

42

57.4M

25.1M

54.7M

22.3M

C

<20M

twice a year

117

1117M

852M

1002M

715M

any time

16

194M

271M

166M

216M

D
S
Total

>20M

twice a year

1

50M

0

50M

0

184

1419M

1148M

1273M

954M

Table 1. Research projects approved in 2007. The maximum points
allotted to the project of each class are the sum of the points for thetwo systems; 1 K point of System-A corresponds to charge for 0.37
hours × node, while 1K point is 0.22 hours × 64CPU for System-B.

ISSP Activity Report 200737

International MegaGauss
Science Laboratory
The aim of this laboratory is to study the physicalproperties of solid-state materials (such as semiconductors,
magnetic materials, metals, insulators, superconducting
materials) under ultra-high magnetic field conditions.
Such a high magnetic field is also used for controlling the
new material phase and functions. Our pulse magnets, atmoment, can generate up to 85 Tesla by non-destructive
manner, and from 100 up to 850 Tesla (the world strongest
as an in-door record) by destructive (the single turn coil andthe electro-magnetic flux compression) methods.
They are opened for 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
our ultimate 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 versatile
physical precision measurements. The available measuring
techniques now involve magneto-optical measurements,
cyclotron resonance, spin resonance, magnetization andtransport 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 other magnetic materials. Non-destructive strong pulse
magnets are expected to provide us with reliable and precise
solid state physics measurements. The number of collaborative groups for the research is over 50 in the year of
2007. Multiple extreme physical conditions combined withultra-low temperatures and ultra-high pressures are alsoavailable.
A 210 MJ flywheel generator which is the world largest
DC power supply (recorded in Guinness book of records in
1907/98) has been installed in the newly build DC Flywheel
generator station at our Institute. The generator, once

Fig. 1. The building for the flywheel generator (right hand side) anda long pulse magnet station (left hand side). The flywheel giant DC
generator is 350 ton in weight and 5 m high (bottom). The generator,
capable of a 51 mega watt out put power with a 210 mega jouleenergy storage, is planned to energize the long pulse magnet generating 100 Tesla without destruction.

38

ISSP Activity Report 2007

disassembled from the one used for Toroidal magnetic fieldcoil in JFT-2M (JAERI Fusion Torus-2M) Tokamak nuclear
fusion testing device, is now renewed as a power supply forthe pulse magnets. The construction of the magnet service
station has also been accomplished. 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 used for the outer-magnet coil torealize a 100 Tesla nondestructive magnet.
Our destructive magnets, such as the single-turn coiland the 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 850 T within a 4 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
in material science realized under such extreme quantum
limit conditions.

Low Energy Excitations in the Vortex
State of the Anisotropic s-Wave
Superconductor CeRu2
K. Machida and T. Sakakibara
It is now well established that zero energy density ofstates (ZEDOS) in the vortex state of d-wave superconductors (SCs) exhibit a characteristic oscillation as a function of
the angle between the magnetic field H and the nodal directions, due to the “Doppler effect” of nodal quasiparticles[1,2] This ZEDOS oscillation, which can be observed by
specific heat C(H) and thermal conductivity measurements
in rotating H, provides a means to determine the gap structures of nodal SCs.
Here we demonstrate that the field rotation experiments
can also be a powerful tool to examine the gap structureof anisotropic s-wave SCs, where the gap amplitude only
modulates on the Fermi surface and does not vanish. The
system we studied is a cubic Laves phase compound CeRu2
with the superconducting transition temperature T c of
6.3 K and the upper critical field Hc2 of 5.2 T [3]. Figure
1 shows the experimental results. When H is rotated in a(001) plane, we observed a clear fourfold oscillation in C(H)(upper panel), which can be expressed in the form:
		
C(H,θ )=C0+CH(1+A4cos4θ ),where C0 and CH denote the field-independent and dependent parts of the specific heat, respectively. θ is the field
angle measured from [100]. The coefficient A4 is the relative
amplitude of the fourfold oscillation, which is strongly H
and T dependent as shown in the contour plot in the lower
panel. It should be noticed that A4 takes the maximum
at finite H, and rapidly diminishes by decreasing H at
T=0.34 K or decreasing T at H=0.5 T.
We have performed microscopic calculations by solving
the Eilenberger equations fully self-consistently assuming
the gap function:		∆(k)= ∆0(1+ α cos4θ ),where the gap anisotropy parameter α is chosen to be

Fig. 2. Landscape of A4(T,H) calculated for the anisotropic s-wave
model with α=0.5. (a) Stereographic view and (b) contour plot.

0.5 to best reproduce the experimental data. Figure 2
shows the results of A4(T,H ), where the upper panel (a)is a stereographic view and the lower panel (b) displays acontour plot. It can be seen clearly that the maximum of
A4 is located at finite T and H. This feature is absent in the
nodal gap SCs where the landscape in A4(T,H) is a simple
peak structure with the maximum located at T=0 and H=0.
The present result is fully understandable because in anisotropic s-wave SCs a finite minimum gap ∆min exists and isovercome either by an applied field or by thermal excitations. Our calculations confirm that CeRu2 is an aisotropics-wave SC having the gap anisotropy ratio ∆min/∆max~0.3
with ∆min located along [110] directions [3].
References[1] I. Vekhter et al., Phys. Rev. B 59, R9023 (1999).
[2] P. Miranovic, M. Ichioka, K. Machida, and N. Nakai, J. Phys.
Condens. Matter 17, 7971 (2005).
[3] A. Yamada, T. Sakakibara, J. Custers, M. Hedo, Y. Onuki,
P. Miranovic, and K. Machida, J. Phys. Soc. Jpn. 76 123704 (2007).
Authors
A. Yamada, T. Sakakibara, J. Custers, M. Hedo a, Y. Onuki b,
P. Miranovicc, and K. Machidad
aUniversity of Ryukyu
bOsaka University
cUniversity of Montenegro
dOkayama University

Ground State in One-Dimensional
Molecular Conductor Exhibiting
Giant MagnetoresistanceN. Hanasaki and H. Tajima
Fig. 1. Angular oscillation of the specific heat in the vortex stateof CeRu2 when H is rotated in the (001) plane (upper panel), and acontour plot of the T and H variation of the fourfold amplitude A4.

The gigantic response of the spin-dependent transport
has made many important contributions to physics andbeen applied to magnetic storage. For the realization of the

ISSP Activity Report 200739

giant magnetoresistance, the intermolecular or intramolecular interaction between the conduction electron andthe local moments is indispensable. In case of the intermolecular interaction between the molecules contributing to
the conduction and the other molecules having the local
moments, it is necessary to control the molecular arrangement precisely in the crystal. The metal-phthalocyanine
molecule is advantageous, since it provides the strong intramolecular interaction. Figure 1(a) shows the structure of theFe(Pc)(CN)2 (Pc=phthalocyanine) molecule. This molecule
has the local moment in the next HOMO (HOMO=highest
occupied molecular orbital), which reflects the d-orbitalof the central Fe atom (red). HOMO consists of the atomic
orbitals of the Pc planar molecule. As displayed in Fig.1(b)[1], in the crystal, the Fe(Pc)(CN)2 molecules stack along thec axis. This molecular overlap provides the one-dimensional
conduction band along the c axis.
In TPP[Fe(Pc)(CN)2]2 (TPP = tetraphenylphosphonium),the giant negative magnetoersistance is observed below
50K, where the resistance increases with lowering thetemperature [2]. It is important to clarify the origin of the
low-temperature insulating state. In order to investigate thecharge state in the ground state, we measured the X-ray
diffraction. Figure 2(a) shows the picture of the diffraction at
6K. Here, the X-ray beam energy and the oscillation angle
were 20keV and 1 (degree), respectively. The vertical direction in Fig.2(a) is nearly parallel to the c axis, which is the
one-dimensional conducting direction. Many spots existingalong the direction perpendicular to the c axis correspondto the Bragg peaks. Besides these peaks, one can find the
diffuse streak in the middle position between these lines of
the Bragg peaks, as indicated by the arrows. This diffuse
streak extends along the direction perpendicular to thec axis. The intensity of these diffuse streaks is six ordersof magnitude smaller than that of the Bragg peaks. We
display the intensity of this diffuse streak as a function of
the position (pixels) along the c axis, in Fig.2(b). The intensity increases with lowering the temperature. This intensity
enhancement coincides with the low-temperature enhancement of the resistance and the Seebeck effect [1]. Thus, this
diffuse streak is related to the mechanism of the insulating
ground state. Taking into account the three-quarter-filled
conduction band in TPP[Fe(Pc)(CN)2]2 and the periodicityof 2 X c of the diffuse streak, the nearest neighbor Coulombinteraction V is responsible for the insulating state. The
crystal structure analysis at 30K suggests no dimerization of
the Pc molecules. The 57Co nuclear quadrapole resonance(the joint research with Takigawa Lab.) in the isostructuralcompound TPP[Co(Pc)(CN)2]2 reveals the very weak charge
disproportionate state [3]. Thus, it is reasonable to consider
(a)

(a)

(b)

Fig. 2. (a) X-ray diffraction pattern in one-dimensional molecular
conductor TPP[Fe(Pc)(CN)2]2. The 4kF diffuse streak is observed in
the positions indicated by the arrows. (b) Intensity of the 4kF diffuse
streak in the central arrow in Fig.2(a) plotted as a function of theposition (pixels) along the c axis.

that the diffuse streak is ascribed to the charge disproportionation (the weak charge order).
Recently, we also observed the enhancement of thedielectric constants by applying the magnetic field at the
low temperatures, where the diffuse streak is observed,
suggesting the magnetic-field-induced melting of the charge
disproportionation, which is a possible origin of the giant
negative magnetoresistance.
References[1] M.Matsuda et al., J. Mater. Chem. 10, 631 (2000).
[2] N.Hanasaki et al., J. Phys. Soc. Jpn. 75, 033703 (2006).
[3] N.Hanasaki et al., J. Phys. Soc. Jpn. 75, 104713 (2006).
Authors
N. Hanasakia, M. Matsuda, H. Tajima, M. Tanabea, Y. Nogamia, andT. Inabeba Dept. of Physics, Okayama University
b Div. of Chemistry, Hokkaido University(b)Accurate Theoretical Evaluation ofRaman Frequency Shift as a Pressure
Gauge in Diamond Anvil Cell
R. Maezono

Fig. 1. (a) Structure of the Fe(Pc)(CN)2 molecule. The central Fe atom(red) has the coordination to the Pc planar molecule and the CN
ligands. (b) Crystal structure of TPP[Fe(Pc)(CN)2]2 viewed from thec axis [1].

40ISSP Activity Report 2007

Diamond anvil cells are used to study condensed matterover a wide range of pressures and temperatures. The rangeof static pressures attainable today extends at least as far as
the conditions prevailing in the center of the earth (>360
GPa). A thorough understanding of the physical properties of diamond at high pressure is of great importance inthe design and operation of such cells, but although therehave been many experimental studies of this material, someproperties, including the equation of state, remain imperfectly characterized.
The equation of state (EOS) can be described over awide range of pressures in terms of the zero-pressure valuesof the equilibrium volume, the isothermal bulk modulus,
and its pressure derivative. The values of the volume andbulk modulus for diamond are well established experimentally over a substantial range of temperatures, but there isconsiderable uncertainty about the pressure derivative ofbulk modulus. A recent study [2] gave 3.0(1) for the derivative at room temperature, although it has been argued thatthe ruby luminescence pressure calibration used in theanalysis of the experimental data should be revised [3]. The
most commonly cited experimental value [4] is 4.0(5), but
the error bar on this result leads to considerable uncertainty
in the EOS at high pressures.
Diamond is highly transparent to electromagnetic radiation over a large range of wavelengths, and the sample
within a diamond anvil cell may be examined in situ underelevated pressure by X-ray diffraction techniques and also
by Raman, Brillouin, and infrared spectroscopies. The
Raman technique in particular has been used extensively to
study the threefold-degenerate zone-center optical phononmode of diamond under pressure. It has been suggested[2] that the volume dependence of the Raman frequency
could be used as a pressure gauge in diamond diamondanvil cell experiments, and more information about the
Raman frequency under high compression would help in thecalibration process.
In view of the unsatisfactory situation regarding ourknowledge of the EOS of diamond and the importance ofthe material, we believe that a study using highly accurate
continuum quantum Monte Carlo (QMC) techniques would
be useful. We have therefore calculated the EOS up to apressure of about 500 GPa and the Raman frequency of
diamond up to about 320 GPa using both the variationaland diffusion quantum Monte Carlo (VMC and DMC)
techniques.
Vinet EOS is used to estimate parameters in EOS, which
has been demonstrated to work well over large pressure
ranges. The values of equilibrium volume and bulk modulus
obtained from the DMC calculations are the closest of thetheoretical values to experiment. The value of the derivativeis estimated as 3.7(1) using DMC. Given the level of agreement between the various theoretical methods including
DFT it seems that the experimental value of 3.0(1) cannot

Fig. 1. The Raman frequency as a function of volume. The shaded
yellow region shows the range of values obtained by using Gruneisenparameters in the range 0.9-1.06.

be sustained. Our QMC results are thus consistent with theideas of Holzapfel [3] regarding the refinement of the rubyluminescence pressure scale used in analyzing diamondanvil data.
We computed the frequency of the first-order Raman
mode of diamond at four volumes corresponding to apressure range of approximately 0–320 GPa using the frozen
phonon method. The volume dependence of the Raman
frequency by our QMC predicts the Gruneisen parameter tobe 0.94(1), providing a gauge to measure high pressure by areliable theoretical evaluation.
References[1] R. Maezono, A. Ma, M. D. Towler, and R. J. Needs, Phys. Rev.
Lett. 98, 025701 (2007).
[2] F. Occelli, P. Loubeyre, and R. LeToullec, Nat. Mater. 2, 151(2003).
[3] W. B. Holzapfel, J. Appl. Phys. 93, 1813 (2003).
[4] H. J. McSkimin and P. Andreatch, Jr., J. Appl. Phys. 43, 2944
(1972).
Author
R. Maezono
School of Information Science, Japan Advanced Institute of Scienceand Technology

Dynamic Nuclear Polarizationin Corbino Geometry
M. Kawamura, T. Machida, and S. Katsumoto
Effect of nuclear spin polarization on the transport
through semiconductor heterostructures is now attracting
much attention. Especially dynamic nuclear polarization(DNP) due to some non-equilibrium phenomenon is an
important candidate as a tool to manipulate nuclear spins
quantum mechanically because it potentially polarizes spinswith very high efficiency without external magnetic field.
DNP occurs, for example, in the breakdown of quantum
Hall states at high biasing currents, which is a limitation of
accuracy in quantum Hall resistance standard. This is also
very convenient for spin manipulation, in that the polarization can be readily detected through the conductance withextremely high sensitivity. In order for this method to be
useful, we should clarify the location (in the samples) andthe origin of DNP.
For the elimination of the possible edge channel originated non-equilibriums, we have adopted the Corbino
geometry (the inset of Fig. 1(b)), where the voltage isapplied radially across the two-dimensional electron
system at an AlGaAs/GaAs hetero-interface and no edge
channel exists in the sample. In Fig. 1, we fixed the external
magnetic field at which the filling factor is 1.05 and swept
the voltage across the sample. The breakdown occurs
around 30 mV and above that we observe finite current
and apparent hysteresis. The latter is due to DNP, whichis evidenced by the response to applied radio frequency
shown in the inset of Fig. 1(a). In the response, a current
dip due to the magnetic resonance of 75As nuclei is evident.
Now we performed a "pump and probe" experiment.
In the procedure, the voltage was swept up to "pumping"voltage, where the system was kept for 900 s. Then thevoltage was abruptly moved to "probing" voltage, which was
fixed at 50 mV in the present experiment, and the transientcurrent increase ΔI was measured. Figure 1(b) shows thus
measured transient current as a function of the pumping

ISSP Activity Report 2007

41

Fig. 1. (a) Device current as a function of the applied voltage. The
blue and red curves correspond to up sweeping and down one,respectively. Apparent hysteresis is observed above 40 mV. The inset
shows the current at 50 mV as a function of applied radio frequency.
Strong dip due to 75As nuclear magnetic resonance is observed.
(b) Transient current as a function of pumping voltage. The probing
voltage is fixed to 50 mV as indicated by the arrow. The inset showsa micrograph of the sample with the Corbino geometry.

voltage. The transient current steeply increases with thepumping voltage around 45 mV, which coincides with therise of quantum Hall breakdown current.
The result indicates that the quantum Hall breakdown
brings about the DNP. Since the breakdown is induced by
the avalanche multiplication of electron-hole pairs due tointer-Landau level impact ionization, we deduce that themultiplication causes the DNP. In an odd-integer quantum
Hall state, the avalanche kicks up electrons between
different spin subbands, resulting in electron spin flips.
The electron spin flips cause nuclear spin flips via hyperfine interaction. Our results demonstrate that such process
occurs in bulk conductance channels and supports theabove inference.

fundamental science and for possible future applications
to devices, catalyses and so on. Among various methods
for controlling self-assembly, the use of specific adsorbatesubstrate interactions on template surfaces is a promisingand general approach to guide the fabrication of large-scale
inorganic or organic nanostructures. The use of surface cues
to guide adsorption processes has been demonstrated on avariety of spontaneously nanostructured substrates. Ordered
nanostructure arrays and thin films with distinct physicaland chemical properties can be achieved on host templates
by the site-specific nucleation of adsorbates and successive
organized growth. In the present study, we use nanopatternsof the Cu(001)c(2×2)-N surfaces, which have been usedas templates for the controlled growth of several metalnanoisland arrays [1], for making periodic nano-assemblies
of fullerene molecules.
A two-dimensional square lattice of nitrogen-adsorbed
areas with a typical lateral dimension of roughly 5 nm [2]can be made when the average density of adsorbed nitrogenatoms on Cu(001) is 35% of that of the surface Cu atoms,
as shown in Fig. 1(a). Narrow strips of the clean Cu surface
periodically separate the nitrogen-adsorbed areas. Nitrogenatoms adsorb on the four-fold hollow site on the Cu(001)lattice, resulting in the Cu(001)c(2×2)-N phase which isimaged as depressed patches with sides running along<010> azimuth orientations.
Figure 1(b) shows the morphology after the deposition of ~ 0.08 ML C60 molecules onto the grid surface at
RT. Here, 1 ML is defined as the coverage of the single
molecular layer. As expected, the fullerenes tend to selectively adsorb on the clean Cu regions due to the relatively
stronger interaction between C60 and Cu, at which chargetransfers from substrate to C60. No nucleation is observedfor C60 at the c(2×2) surface. Thus, the preferential nucleation indicates weaker interaction of the molecule with theReferences[1] M. Kawamura, H. Takahashi, S. Masubuchi, Y. Hashimoto,
S. Katsumoto, K. Hamaya, and T. Machida, J. Phys. Soc. Jpn. 77,
023710 (2008).
Authors
M. Kawamuraa, T. Machidaa, and S. Katsumoto
aInstitute of Industrial Science, University of Tokyo

Fullerene Nanomesh on Nitrogenmodified Cu(001) Surface
F. Rosei, K. Sakamoto, and F. Komori
Controlled self-assembly of molecular nanostructures
has been studied both for elucidating its mechanism in

42

ISSP Activity Report 2007

Fig. 1. STM images showing a N-adsorbed grid Cu(001) surface (a),nucleation of C60 molecules onto the grid surface at RT (b), C60
molecular nanomesh on the grid surface (c), and a single layer film of
C60 on N-saturated Cu(001) surface with nanotrench structures(d). In(a), N-adsorbed square areas are imaged low, and separated by cleanCu surface, which is imaged high. Fullerenes first nucleate at wideand clean Cu areas (b), then cover the whole clean Cu surface (c),and finally make a single C60 layer on the grid surface of N-adsorbed
and clean Cu areas with increasing the coverage. Fullerenes form asingle molecular layer with maintaining the substrate nanostrucruresboth on the grid and N-saturated (d) Cu(001) surfaces.

c(2×2)-N surface than with the clean Cu surface. The
deposited C60 can migrate freely on the c(2×2) area at RT.
Selective nucleation on this nanopatterned surface has beenpreviously reported for the deposition of various metals,
and is expected to be a fairly general behavior [1].
An increase of C60 coverage to ~ 0.28 ML leads to thesaturated adsorption of C60 on the clean Cu areas forming a
2D C60 molecular nanomesh with the single molecular layerheight as shown in Fig. 1(c). This 2D nanomesh follows thegrids of the template and thus is highly regular. Further
deposition gives rise to the growth of C60 on the c(2×2)-N
surface until the first molecular layer is completed. The
growth of C60 on this nanopatterned surface is different
from metal growth on the same surface; in this case metalnanoislands grow up to 2 ML on the grid without wetting
the c(2×2)-N surface [1]. Further deposition of C60 results inthe layer-by-layer growth of a C60 thin film.
On the N-saturated Cu(001) surface, C60 molecules
grow also with a layer-by-layer mode keeping the substratenanostructure as in Fig. 1(d). They thermally desorb at 400
K, and thus the interaction at the interface is a van der
Waals force. The weak interface interaction can stabilize thesubstrate grid-nanopattern even after the multilayer growthof C60. This is in contrast to the metal growth on the same
surface, where nitrogen-atoms segregate to the surfaces ofthe deposited metal [3].
References[1] F. Komori, S. Ohno, and K. Nakatsuji, Prog. in Surf. Sci. 77, 1(2004).
[2] F. M. Leibsle, C. F. J. Flipse, and A. W. Robinson, Phys. Rev. B
47, 15865 (1993).
[3] D. Sekiba, S. Doi, K. Nakatsuji, and F. Komori, Surf. Sci. 590,
138, (2005).
Authors
B. Lu, T. Iimori, K. Sakamotoa, K. Nakatsuji, F. Roseib, andF. Komori,aGraduate School of Advanced Integration Science, Chiba University
bINRS-EMT, University of Quebec

Resistance Switching in
Oxide Heterostructures
I. Ohkubo and M. Lippmaa
Resistance switching in oxides is a phenomenon where
the resistance of a material changes reversibly by the application of a large electric field. Depending on the type ofmaterial and the structure of a device, several different
mechanisms can be at play, such as the formation of
conducting filaments, modulating the height of a Schottky
barrier, storing charge in trap states, etc. While resistanceswitching is at the heart of new nonvolatile memory development, it also highlights the need to understand the basic
physical processes that govern the transport propertiesof nanoscale oxide layers, namely anion and cation diffusion, defect formation, and charge accumulation. Of special
interest is how nonvolatile electronic or structural changes
can be driven by electrostatic field.
One suitable material for resistance switching experiments is Pr0.7Ca0.3MnO3 [1,2]. Earlier work has shownthat the resistance change originates from the interface
layer between the manganite film and an Aluminumelectrode [3,4]. The basic switching structure is shown in
Fig. 1, together with the time dependent resistance change

Fig. 1. Top: Structure of the resistance switching devices grown on(LaAlO3)0.3-(Sr2AlTaO6)0.7 (LSAT) substrate. The bottom electrodeis a metallic LaNiO 3 layer. Resistive switching occurs in thePr0.7Ca0.3MnO3 (PCMO) layer. As shown in the time-dependent
switching characteristics, smaller devices can be switched faster byapplying positive or negative voltage pulses to the top Al electrode.

for different device sizes. The static high or low resistance states can be obtained by applying short positiveor negative 'write' pulses to the device. As shown by theswitching data in Fig. 1, the switching time becomes smaller
as the devices are scaled to smaller size, which meansthat when scaled to suitable small feature size, it may bepossible to achieve ns-scale switching speeds.
Although a trap-controlled space-charge-limited current
mechanism has been identified as the most likely candidate
for explaining the resistance change, the precise reason why
the effect only appears at a manganite-aluminum interface
remains a subject of atomic-scale interface studies. It isas yet not clear how strong electric fields drive structuralchanges in oxide heterostructures. Future work within thiscollaboration aims to use the resistance switching effect asa tool for detecting field-driven structural changes in oxide
nanostructures.
References[1] A. Maniwa et al., J. Magn. Magn. Mater. 310, 2237 (2007)[2] H. Wadati et al., J. Magn. Magn. Mater. 310, 963 (2007)[3] K. Tsubouchi et al.., Adv. Mat. 19, 1711 (2007)[4] I. Ohkubo et al., Mat. Sci. Eng. B 148, 13 (2008)
Authors
I. Ohkubo a , H. Kumigashira a,e , A. Fujimori b,c , M. Oshima a ,H. Wadatib,c, A. Maniwaa, K. Okanoa, K. Tsubouchia, Y. Matsumotod,
K. Itakae,f, T. Ohnishi, T. Haradaa, M. Kawasakig, H. Koinumae,f,h,and M. Lippmaa
a Dept. of Applied Chemistry, University of Tokyob Dept. of Physics, University of Tokyoc Dept. of Complexity Science and Engineering, University of Tokyod Materials and Structures Laboratory, Tokyo Institute of Technology
e CREST, Japan Science and Technology Corporation
f Graduate School of Frontier Sciences, University of Tokyo
g Institute for Materials Research, Tohoku University
h National Institute for Materials Science

ISSP Activity Report 200743

Mechanical Spin Pumping inSuperfluid 3He A1 phase
H. Kojima and H. Ishimoto
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 mostimportant aspect of the A1 phase is that its superfluid
component is totally spin-polarized along the magnetic field.
It is a kind of ferromagnetic superfluid. A mass superflow isthen simultaneously a spin flow. The phase transition into
the A1 phase is accompanied by the spontaneous breakingof relative spin-gauge 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 experimentson this interesting magnetically driven superflow show apeculiar spin relaxation that is dependent on temperatureand magnetic fields [3]. The results can be interpreted interms of intrinsic spin relaxation based on Leggett and
Takagi theory [4] and the predicted presence of small but
increasing presence of minority spin pair condensate in A1
phase [5].
In these measurements, we recognized a mechanicalspin pumping and found a new method to derive thespin relaxation time in the A1 phase. A sample cell has
a large reservoir that is connected to a small detector
chamber through a super leak made of three channels ofwidth 18 μm. A flexible Myler membrane dividing the twochambers forms a capacitance with a fixed electrode. It
works as a very sensitive differential pressure sensor andalso as a pump to produce a polarized spin flow into thedetector chamber. A pulsed large DC voltage (about 30 V)
on the capacitance sensor induces a simultaneous mass andspin superfluid flow into the small chamber (spin pump).
After thermal equilibrium, release of the DC voltage causesa sudden pressure drop. The sudden drop (∆P) is a consequence of reversed superfluid flow through the superleak. It
is compensated by the produced spin density difference ∆S). In the A2 phase, ∆P suddenly returns to zero, whereas in
the A1 phase there still remains a slow relaxation (Fig. 1).
This slow relaxation is due to spin relaxation that is peculiar
to A1 phase. The spin relaxation times derived from theslow decay times are in good agreement with those obtainedin the magnetic fountain effect. This fact supports ourFig. 1. Membrane’ s displacement corresponding to the voltagechange in the A1 , A2 and normal phase at 21 bars and 8T. (A1: red,A2: green, normal: black)

44

ISSP Activity Report 2007

Fig. 2. The spin relaxation rate derived from mechanical effects at 21bars and various magnetic fields as a function of reduced temperature.

interpretation that the observed slow relaxation stems fromspin relaxation. After a simple analysis, a device independent intrinsic spin relaxation rate is obtained as shownin Fig. 2. The temperature dependence agrees pretty wellwith the above theoretical estimation, although the amountof the minority spin condensate seems to be smaller than
predicted.

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, Annals of Physics 106, 79 (1977).
[5] H. Monien and L. Tewordt, J. Low Temp. Phys. 60, 323 (1985).
Authors
A. Yamaguchi, K. Suzuku, Y. Aoki, H. Ishimoto, and H. Kojimaa
aSerin Physics laboratory, Rutgers University

Discovery of Coherent Precessionof Magnetization in Superﬂuid
3He-A-phase *Yu. M. Bunkov, T. Mizusaki, and M. Kubota
We report the ﬁrst observation of coherent quantum
precession (CQP) of magnetization in superﬂuid 3He-A inaerogel [1]. The coher- ent precession in bulk 3He A-phase
is un-stable due to the positive feedback of spin supercurrent to the gradient of phase of pre- cession. It waspredicted that the homogene-ous precession will be stable
if the orbital momentum of 3He-A could be oriented along
the magnetic ﬁeld [2]. We have succeeded to prepare thisconﬁguration by emerging 3He in uniaxially deformed anisotropic aerogel [3].
Superfluid 3He is a unique superfluid composed of p
type Cooper pairs. Because of large internal freedom of
the Cooper pairs, there are multiple superfluid phases andso on. The superfluid wave function can be expressed asa product of mass, orbital momentum and magnetization(spin) components. The coherent precession of magnetization was observed early in superﬂuid 3He-B [4]. Dueto the concave shape of dipole-dipole interaction andnegative feed-back of spin supercurrent (the quantum
flow of magnetization due to the gradient of the phase of* Prof. Yuryi Bunkov has been selected for a Fritz London Prizewinner 2008, together with the coauthors of reference[4] and thepresent work is an extension of their original finding in superfluid
3
He B phase in 1984 into superfluid 3He A phase, which has been
searched for ever since that time.
References[1] T. Sato et al., arXiv:0804.2994, and submitted to PRL.
[2] Yu. M. Bunkov and G. E. Volovik, Europhys. Lett. 21, (8) 837(1993).
[3] T. Kunimatsu et al.,JETP Lett. 86, 216 (2007).
[4] A. S. Borovik-Romanov, Yu. M. Bunkov, V. V. Dmitriev, and Yu.
M. Mukharskiy, JETP Lett. 40, 1033 (1984); I. A.Fomin, JETP Lett.
40, 1036 (1984).
[5] Yu. M. Bunkov and G. E. Volovik, Phys. Rev. Lett. 98, 265302(2007).
[6] T. Kunimatsu et al., J. Low Temp. Phys. 150, 435 (2008).
Fig. 1. Formation of the coherent precession of magnetization; theCQP in A-like phase at 0.8Tca (labeled by A’ ) and the HPD in B
phase at 0.7Tca (labeled by B). The solid curves are taken at an rfﬁeld (3volts) for upward sweep and the dotted one for downward
sweep. The relative positions to Larmor fre- quency(marked as 0) are
just as expected.

spin part of order parameter), the coherent precessionof magnetization in 3He-B arises spontaneously even in
inhomogeneous magne-tic ﬁeld, as was discovered in1984
by Borovik- Romanov et al. [4]. This eﬀect was named a
Ho-mogeneously Precessing Domain (HPD), due to thesplitting of the magnetization in the cell into two domains,
stationary one and the other with the coherent precessionof magnetization deﬂected by the angle slightly above themagic angle of 104°. Recently the HPD was identiﬁed as
magnon Bose-Einstein condensation by Bunkov and Volovik[5]. Here we report the ﬁrst observation of the Coherent
Quantum Precession (CQP) of magnetization in A-likePhase in uniaxially deformed aerogel, where the l-vector
in the orbital part of the order parameter is oriented along
the magnetic ﬁeld [3,6]. We call the coherent precessionin A-phase as the CQP, distinguishing it from the HPD in
B-phase. CQP has been searched for for a long period oftime, but in bulk A phase l-vector tends to be perpendicular
to magnetic field H. CQP can appear only under a special
condition when l-vector is forced to be in parallel with H.
This has been realized in 3He-A (see Fig.1, 2) immersed
in a uni-axially deformed aerogel [3]. A basic diﬀerencein the observation is that in CQP the entire magnetization
precesses uniformly with a tipping angle β determined byfrequency sweep Δ f from cw NMR, while the HPD precession occurs in a domain with β >104°.

Fig. 2. The normalized amplitude of NMR signal by M ⊥ (β =90° )while sweeping frequency upward at dif- ferent excitations vrf (a:0.1V, b: 0.5V, c: 1.5V, d: 3V, e: 4V). The dashed line corresponds tothe theoretical dependence of M ⊥ on the tipping angle dependent
frequency shift given by ∆ω = − (Ω2A/2ωL) cosβ with the maximum
frequency shift chosen at the peak of signal a and the dotted line
corresponds to that for the maximum frequency shift chosen at theright edge of signal a. See details in [1].

Authors
T. Sato, T. Kunimatsua, K. Izumina, A. Matsubaraa,b O. Ishikawac,
Y. Sasakib, M. Kubota, T. Mizusakia,b, and Yu. M. Bunkovd
a Department of Physics, GraduateSchool of Science, Kyoto
University
bResearch Center for Low Temperature and Materials Sciences,
Kyoto University
cDepartment of Physics, GraduateSchool of Science, Osaka City
University
dMCBT, Institut N´eel, CNRS/UJF

Pressure Effect on theElectronic State in CeTl3
T. Endo, R. Settai, and Y. Uwatoko
When pressure is applied to cerium-based magnetic
compounds, various interesting phenomena such as
non-Fermi liquid behavior, heavy fermion state andpressure-induced superconductivity appear in the vicinityof the quantum critical point where the Néel temperature
TN is suppressed to zero. CeTl3 is an antiferromagnet with

Fig. 1. (a) Temperature dependence of the electrical resistivity underpressure in CeTl3 and (b) Pressure phase diagram of the Néel temperature TN in CeTl3.

ISSP Activity Report 200745

References[1] R. A. Elenbaas et al., J. Magn. Magn. Mater. 15-18, 1218 (1980).
[2] N. D. Mathur et al., Nature 394, 39 (1998).
[3] I. Umehara et al., J. Phys. Soc. Jpn. 60, 591 (1991).
Authors
T. Endoa, M. Nakashimab, R. Settaia, D. Aokic, Y. Ōnukia, andY. Uwatoko
aGraduate School of Science, Osaka University
bDepartment of Physics, Faculty of Science, Shinsu University
cDRFMC/SPSMS, CEA-Grenoble, France

Motional Behavior of
Fluorobenzene Guests Imprisoned in a
Hofmann-dahxn Clathrate 1D Cavity
A. Nagahara, S. Nishikiori, and O. Yamamuro

Fig. 2. (a) FFT spectra under pressure and (b) pressure dependenceof the cyclotron effective massin CeTl3

TN = 3.9K [1]. CeTl3 is a good reference compound for an
antiferromagnet CeIn3, which exhibits the pressure-induced
superconductivity at 0.2 K around the critical pressure
Pc = 2.5 GPa [2]. We studied the electrical resistivity underpressure in CeTl3 using a cubic anvil cell up to 8 GPa.
Figure 1(a) shows the temperature dependence of theelectrical resistivity under several pressures in CeTl 3.
A shoulder-like resistivity peak around 50 K, which isdue to the combined phenomenon between the crystalline electric field and Kondo effects, is enhanced withincreasing pressure. The electrical resistivity at 8GPa istypical for heavy fermion compounds such as CeCu6. Néel
temperature TN, which is indicated by an arrow, is found to
decrease with increasing pressure, ranging from TN = 3.9 K
at ambient pressure to 2.4 K at 6GPa. The antiferromagnetic
ordering was not observed at 8GPa because the measurement was carried out down to about 2 K. We plotted the
Néel temperature as a function of pressure in Fig. 1(b).
The critical pressure Pc was not well defined in the present
experiment, but most likely estimated to be about 10GPa.
In order to investigate the change of the electronic state
under pressure in CeTl3, we measured the de Haas-van
Alphen (dHvA) effect under pressure. Figure 2 shows (a)the fast Fourier transformation (FFT) spectra under pressureand (b) the pressure dependence of the cyclotron effective
mass of the dHvA branches. The observed dHvA branches
are similar to those of LaIn3. This result indicates that the
4f-electron in CeTl3 is localized.The dHvA frequenciesare
almost unchanged under pressure. On the other hand, thecyclotron masses increase with increasing pressure. The
increase of the cyclotron mass reflects the approach to thequantum critical point by applying pressure. Further study
below 2 K at around 10 GPa is necessary to investigate thequantum critical behavior such as pressure-induced superconductivity.

46

ISSP Activity Report 2007

The state of a system in which molecules are interactingwith each other has been an important research target invarious viewpoints. Many variations and situations are
considered for such systems and many cases have been
widely investigated. We here examined a simple case as
following. Polar molecules are arrayed one-dimensionally.
The molecules can undergo not translational motion but
reorientational motion (Fig. 1). Simply saying, this situation
is similar to 1D Ising model made with macro species.
To realize the above system we used a clathratecompound. Clathrate compounds are formed with a hostand guests. The host is a kind of cage and the guests are
imprisoned in the host. Depending on clathrate hosts there
are many structural variations. We choose the Hofmanndahxn type clathrate [1] including fluorobenzene (FBz) as
guests, Cd(dahxn)Ni(CN)4·FBz. The host of the clathrate is ametal complex of Cd(dahxn)Ni(CN)4 which has a 3D framework structure made with octahedral Cd(II), square planar
Ni(II) and bidentate CN- and 1,6-diaminohexane (dahxn).

Fig. 1. 1D array of polar molecules which are allowed to perform nottranslational but reorientational motion.

Fig. 2. Crystal structure of Cd(dahxn)Ni(CN)4·FBz at 153K. Crystal
data: C16H21N6FCdNi, monoclinic, P2/m, a = 7.0894(3) Å, b =7.5993(3)Å, c = 9.3698(7) Å, β = 103.144(2)°, Z = 1. All FBz guests
are on the plane of y =1/2. The orientation of each FBz guest is
distributed to two inverted directions. H atoms are omitted forclarity.

References[1] T. Iwamoto, Comprehensive Supramolecular Chemistry, ed. J. L.
Atwood, J. E. D. Davies, D. D. MacNicol, F. Vögtle, and J-M. Lehn
(Pergamon, Oxford, 1996), vol. 6, ch. 19, pp 643-690; T. Iwamoto, J.
Inclu. Phenom. 24, 61 (1996).
Authors
A. Nagaharaa, S. Nishikioria, and O. Yamamuro
aDepartment of Basic Science, Graduate School of Arts and Sciences,
The University of Tokyo

Fig. 3. Temperature dependence of dielectric permittivity forCd(dahxn)Ni(CN)4·FBz.

Figure 2 shows the crystal structure of the clathrate. In the
3D framework host a 1D channel-like cavity with a sectionof ca. 7.6 Å × ca. 9.2 Å running straightly along the a axisof the crystal is formed. In this channel-like cavity FBz
guests, whose dipole moment is 1.63 D, are lined up along
the a axis at regular intervals. The molecular planes of all
guests in the cavity are on a plane which is parallel to theac plane and is as y =1/2.
The single crystal X-ray diffraction experiments at 298 K
and 153 K revealed that the orientation of the FBz guests
is distributed to two inverted directions. 2H-NMR powder
patterns measured on the clathrate including deuterated
FBz showed that the guests undergo reorientation between
the two inverted orientations at least above 123 K. This
motional mode is similar to that of the spin in Ising model.
To elucidate the motional behavior of the guests inlower temperature region dielectric permittivity wasmeasured by using a homemade cryostat for dielectricmeasurements. Powdered sample was packed in a cylindrical cell and the measurement was carried out between
300 K and 6 K in temperature and between 10-1 Hz and
106 Hz in frequency. Figure 3 shows the real part of thecapacitance observed. Two dielectric dispersions and nosign of phase transition can be found at once. The large
dispersion ranging from 200 K to 70 K corresponds to theinversion motion observed in the 2H-NMR spectra. If theorientation of the guests falls into an ordered state, a firstorder phase transition accompanied with a change of thecrystal structure must take place. However, no such sign
was observed. From 40 K to 10 K a small dispersion wasobserved. Appearance of dispersion suggests that molecular motion is thermally activated. The small dispersion
indicates that the guests undergo thermal motion even at
10 K. This motion is considered to be a vibrational reorientation at the bottom of the potential surface for the inversion motion in the higher temperature region. The guests
are hardly considered to climb over the potential wall andto form an ordered state at this low temperature. Perhaps,
this disordered state is not dissolved and the system falls
to a glassy state before reaching 0 K. Formation of a
glassy state is not unusual for macro systems. However,such transition usually takes place in higher temperature
region. No freezing even at ca. 10 K observed in our macrosystem is a rare case. Although this system is resemble to
1D Ising model, three-dimensional molecular interaction
from surroundings actually exists more or less because oursystem is a real object. Perhaps, the structure of this clathrate host cancels or reduces the three-dimensional interaction to bring the unusual phenomenon observed here.

TEM Study of the Two-Dimensional
Quantum Antiferromagnets(CuCl)LaNb2O7 and (CuBr)Sr2Nb3O10
H. Kageyama, M. Ichihara, and Y. Ueda
Chimie douce, solid-state reactions at relatively low
temperatures, i.e., away from thermodynamic equilibrium
offer rational design of the magnetic lattices in nonmolecular solids. Recently, various exotic quantum magnetic
phenomena have emerged from a new class of S = 1/2
layered transition-metal oxyhalides (CuX)[An-1B nO 3n+1]––(where X = Cl , Br , A = La3+, Ca2+, Na+…, B = Nb5+, Ta5+,
4+
Ti …, n = 2, 3), obtained by low-temperature ion-exchange
reactions [1]. They range from collective singlet-groundstates in (CuCl)LaNb2O7 (Fig. 1(a)) [2-4], a collinear order at
32 K with a reduced magnetic moment in (CuBr)LaNb2O7[5], to successive phase transitions and 1/3 magnetization
plateaus in (CuBr)Sr2Nb3O10 (Fig. 1(b)) [6], which may bemapped onto the so-called J1-J2 model.
In order to obtain universal understanding of the magnetism in this series of materials, precise structural analysis
is required. Considering that single crystals are not in ourhands (since they are metastable compounds and hence
could not be grown by high temperature melting method),transmission electron microscopy (TEM) will offer crucial
information on the space group, as well as possible superstructures. The TEM experiments were carried out typicallyat room temperature using a JEM2010F system with anoperating voltage of 200 kV. The specimen was finely
ground in methanol and then placed on a Cu microgrid
mesh for TEM observation
Shown in Fig. 2(a) is the [001] zone lattice image of(CuCl)LaNb2O7 [7] that demonstrates contrast with a special

F i g . 1 . C r y s t a l s t r u c t u r e o f ( a ) ( C u C l ) L a N b2O 7 a n d ( b )(CuBr)Sr2Nb3O10, where the CuCl and CuBr layers providing the S= 1/2 square lattice are magnetically separated by the non-magnetic
perovskite slab of n = 2 LaNb2O7 and n = 3 Sr2Nb3O10, respectively.

ISSP Activity Report 2007

47

Single Crystal Growth of a New
Pyrochlore Frustrated Magnet Pr2Zr2O7
by the Floating Zone Method
K. Matsuhira and Z. Hiroi

Fig. 2. High-resolution transmission electron microscopy image of(CuCl)LaNb2O7 at room temperature, obtained along the [001]-zone
axis and the corresponding electron diffraction pattern, whereindices are given based on the primitive unit cell for the doublelayered perovskite.

period of about 0.4 nm along <100>, consistent with thelattice parameter. However, the corresponding electron
diffraction (Fig. 2(b)) has revealed weak reflections suchas (1/2, 0, 0) or (0, 1/2, 0), in addition to strong fundamental reflections relevant to the reported crystal structure.
The weak reflections are commensurate and indicate thedoubling of the lattice period of both a- and b-axes, i.e.,the size of the unit cell is given by 2a × 2b. Such a superstructure has not been detected even by high-Q resolution synchrotron X-ray diffraction, presumably due totiny modulation of the atoms and/or small domain size. A
similar superstructure has been recently obtained by the
TEM study of (CuBr)Sr2Nb3O10 [8]. It is considered thatthe superstructure formation, which give a deviation of thesimple J1-J2 model, plays crucial role in the spin-singlet
state in (CuCl)LaNb2O7 and the 1/3 magnetization plateauin (CuBr)Sr2Nb3O10 is still not clear.
References[1] 陰山洋，北野太郎，大場紀章，網代芳民，吉村一良，西正和，廣田和馬，鳴海康雄，金道浩一，萩原政幸，固体物理 41, 129 (2006).
[2] H. Kageyama, T. Kitano, N. Oba, M. Nishi, K. Hirota, L. Viciu,
J. B. Wiley, J. Yasuda, Y. Ajiro, and K. Yoshimura, J. Phys. Soc. Jpn.
74, 1702 (2005).
[3] H. Kageyama, J. Yasuda, T. Kitano, K. Totsuka, Y. Narumi,
M. Hagiwara, K. Kindo, Y. Baba, N. Oba, Y. Ajiro, and K. Yoshimura,
J. Phys. Soc. Jpn. 74, 3155 (2005).
[4] A. Kitada, Z. Hiroi, Y. Tsujimoto, T. Kitano, H. Kageyama,
Y. Ajiro, and K. Yoshimura, J. Phys. Soc. Jpn. 76, 093706 (2007).
[5] 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, 113601 (2006).
[6] 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. 76, 063711 (2007).
[7] M. Yoshida, N. Ogata, M. Takigawa, J. Yamaura, M. Ichihara,
T. Kitano, and H. Kageyama, J. Phys. Soc. Jpn. 76, 104703 (2007).
[8] Y. Tsujimoto, Y. Baba, T. Watanabe, A. Kitada, H. Kageyama,
Y. Ajiro, K. Yoshimura, M. Ichihara, and Y. Ueda, submitted to Solid
State Science.

Geometrical frustration can lead to novel phenomena
such as a macroscopic degeneracy in the ground state
and a spin freezing with no long-ranged ordering (LRO).
Pyrochlore compounds have been attracting a great dealof interest because spins reside on the vertices of cornershared tetrahedra (Fig.1). A strong frustration effect is
expected in the pyrochlore magnets.
Recentry, we revealed that the pyrochlore oxide
Pr2Zr2O7 is a local <111> Ising pyrochlore antiferromagnet(Curie-Weiss temperature ΘCW=− 0.55 K). The magnetismof Pr2Zr2O7 arises from Pr3+ (4f 2, J=4) ions, as Zr4+ (4d0) is
non-magnetic. The polycrystalline sample does not exhibit
any LRO at least down to 76 mK. Instead, a spin freezing
behavior is observed below 0.3 K [1]. The crystal electricfield ground state is non-Kramers doublet with a local <111>
Ising magnetic anisotropy. Theoretically, the antiferromagnetic ground state of a single tetrahedron of spins witha local <111> Ising magnetic anisotropy consists of alternate tetrahedra with 4 spins in or 4 spins out (Fig. 1) [2].
However, LRO with 4 spins in or 4 spins out have not yet
been reported in the pyrochlore magnets so far. The local<111> Ising pyrochlore antiferromagnet is firstly reported in
Tb2Ti2O7 [3]. Tb2Ti2O7 remains in a fluctuating paramagnetic spin-liquid state down to 70 mK. Why does not the<111> Ising pyrochlore antiferromagnet indicate LRO?
This question is a fundamental problem in the frustrated
magnetism.
We consider that Pr2Zr2O7 is a key compound to solve
the problem. We need a good single crystal of Pr2Zr2O7 toperform various measurements. Single crystal growth of Zr
pyrochlore oxides has not been reported so far. We have
performed the single crystal growth of pyrochlore titanates(Ln2Ti2O7: Ln=Gd, Tb, Dy, Ho) by the floating-zone method
using an infrared furnace equipped with four halogen lamps(4×1.5kW) and elliptical mirrors so far. However, we could
not form a melt zone in the same way because the melting
point of Pr2Zr2O7 is higher. Next, we tried to use an infrared
furnace equipped with four Xenon lamps (4×3kW) andelliptical mirrors. We encountered some difficulties due toAuthors
H. Kageyamaa, Y. Ajiroa, K. Yoshimuraa, M. Ichihara, and Y. Ueda
aKyoto University

Fig. 1. Pyrochlore lattice: In Pyrochlore oxides A2B2O7, both A and B
sites form the corner-shared tetrahedral network. Antiferromagnetic
ground states (4 spins in or 4 spins out) of a single tetrahedron of
spins with a local <111> Ising magnetic anisotropy are shown.

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ISSP Activity Report 2007

Fig. 2. Single crystal of pyrochlore oxide Pr2Zr2O7.

the high melting point. The biggest problem was the lackof Pr site in the single crystal due to the evaporation of
Pr2O3. In order to avoid the lack of Pr site, we prepared the
Pr-enriched samples in the starting composition.
We have succeeded for the first time in growing a goodsingle crystal of Pr2Zr2O7 after much trial and error. The
crystal is shown in Fig. 2. The crystal was grown under O2
gas flow to avoid oxygen deficiency. The growth rate was
4.5 mm/h. The powder XRD pattern shows the pyrochlore
phase. The SEM-EDS analysis indicated that the ratio of
Pr/Zr is 1.00 in the top part of the single crystal. Therefore,
the good quality of this crystal was confirmed. Various
measurements to clarify the magnetic properties are
currently in progress.
References[1] K. Matsuhira, C. Sekine, C. Paulsen, M. Wakeshima, and
Y. Hinatsu, Physical Society of Japan 2007 Spring Meeting(20aTB-8).
[2] S. T. Bramwell and M. J. Harris, J. Phys.: Condens. Matter 10,
L215 (1998).
[3] J. S. Gardener, S. R. Dunsiger, B. D. Gaulin, M. J. P. Gingras,
J. E. Greedan, R. F. Kiefl, M. D. Lumsden, W. A. MacFarlane, N. P.
Raju, J. E. Sonier, I. Swainson, and Z. Tun, Phys. Rev. Lett. 82, 1012
(1999).
Authors
K. Matsuhiraa, Z. Hiroi, T. Kitazawa, Y. Kiuchi, S. Takagi a
aKyushu Institute of Technology

BiMnO 3 is among the best known ferromagnetic
and ferroelectric multiferroic materials. The centrosymmetric orthorhombic structure Pbnm at high temperature
undergoes a phase transition to a non-centrosymmetricmonoclinic one C 2 around 750-770K and a magnetictransition from the paramagnetic to ferromagnetic phaseat about 100K. The multiferroic monoclinic crystal determined by a neutron diffraction measurement can be seen as
extremely deformed perovskite structure. A first-principles
calculation for monoclinic BiMnO3 [1] shows that the dγ
orbital extended along the Mn-O bond elongated by the
Jahn-Teller effect is only occupied, forming antiferro orbital
order as shown in Fig. 1, and that the ferromagnetic stateis more stable than the antiferromagnetic. It is found basedon a frozen-phonon calculation that the covalent bonddue to hybridization between the Bi-p and O-p orbitals
results in off-centering instability. However, two kinds of Bi
show almost opposite displacement to each other and theresultant electric polarization turns out to be quite small(<0.01C/m2).
PbVO3 and BiCoO3 were synthesized experimentallyby the high-pressure technique and show large tetragonal
distortion and off-centering displacements. The main issue
here is how the energy gaps are formed for the d1 (d6)configuration in V4+ (Co3+) in relation to the large tetragonal
distortion. It is found in a first-principles calculation [2]that the tetragonal distortion together with the observed
off-centering displacement introduces the opposite crystalfield splitting, lower xy and higher (yz, zx), to realize an
insulating electronic structure. In addition, an antiferromagnetic coupling may take place between the neighboring xy
states via O-pπ on the ab plane, resulting in stable C-type or
G-type antiferromagnetic order. The stability of the C-typeor G-type antiferromagnetic order has been confirmed by
the total-energy results calculated for different magnetic
structures. Two instability modes to off-centering displacements are obtained by frozen-phonon calculations for the
tetragonal centrosymmetric structure. One is the modein which the transition-metal ion moves in the opposite

First-Principles Study ofMultiferroic Oxides
T. Oguchi, T. Shishidou, and Y. Uratani
Materials which have more than one ferro orders are
originally called “multiferroics” and may be possibly applied
not only to multi-value devices but also to novel response
phenomena originating from the cross correlation between
different ferro orders. For example, the magnetic responseto an electric field and the electric response to an magnetic
field are known as magneto-electric or electro-magnetic
effect, and a cross correlation between the electric polarization and the lattice distortion is as piezoelectric effect.
Nowadays, materials with a cross correlation between
different order parameters are generally called multiferroics.
Here we report first-principles studies of the multiferroicoxides consisting of ferro (or antiferro) magnetism and ferroelectricity simultaneously. Several perovskite-type oxides
are well known as typical multiferroics. By investigating theelectronic structure of the multiferroic and related materials
and by elucidating the microscopic mechanisms of multiferro orders, new candidate materials are proposed.

Fig. 1. Schematic view of the orbital ordering of Mn-d in BiMnO3.
Arrows indicate the occupied dγ orbital directions at the Mn sites,of which three kinds are denoted by 1, 2 and 3. Open circles denote
the O sites.

ISSP Activity Report 200749

direction to the O octahedron and the other is that Pb or
Bi ion is displaced against the octahedron including thetransition-metal ion. Actual stable structure observed canbe regarded as a superimposed one of these two instability
modes. From the Berry-phase calculations, the electric
polarization is predicted to be 1.52C/m2 for PbVO3 and1.79C/m2 for BiCoO3.
On the basis of the knowledge deduced from the firstprinciples calculations stated above, new multiferroicoxides with ferromagnetism and ferroelectricity have been
designed [3]. The target materials are chosen to be doubleperovskite oxides with Bi at the A site, Bi2BB'O6, where B
and B' are transition-metal ions with the finite number ofd electrons. In the double-perovskite structure, two kinds ofthe transition-metal ions are located in a NaCl-type manner,
where the neighboring B and B' ions form 180º structure
via O ion. The super-exchange coupling between the neighboring B and B' is ferromagnetic only for d 3-d 5 and d 3-d 8
combinations, according to the Goodenough-Kanamori
rule. The cases satisfying both conditions are Cr3+-Fe3+ andV2+-Co4+ for d 3-d 5, and Mn4+-Ni2+ and Cr3+-Cu3+ for d 3-d 8.
First-principles calculations for the cubic double-perovskite
oxides with these combinations predict that, in Bi2MnNiO6,
a stable ferromagnetic solution with d 3 and d 8 configurations is realized with zero-gap electronic structure and finite
energy gaps may be expected by further lattice distortiondue to ferroelectric instability. An experimental explorationof new double-perovskite multiferroic oxides has been madeindependently by using the high-temperature techniqueand has found that Bi2MnNiO6 is multiferroic [4]. A firstprinciples calculation for the observed monoclinic structure
shows that the ferromagnetic state is more stable than theferrimagnetic one and the electric polarization is found tobe 0.28C/m2.
References[1] T. Shishidou, N. Mikamo, Y. Uratani, F. Ishii, and T. Oguchi,
J. Phys.: Condens. Matter 16, S5677 (2004).
[2] Y. Uratani, T. Shishidou, F. Ishii, and T. Oguchi, Jpn. J. Appl.
Phys. 44, 7130 (2005).
[3] Y. Uratani, T. Shishidou, F. Ishii, and T. Oguchi, Physica B 383, 9(2006).
[4] M. Azuma, K. Takata, T. Saito, S. Ishiwata, Y. Shimakawa, and
M. Takano, J. Am. Chem. Soc. 127, 8889 (2005).
Authors
T. Oguchia, T. shishidoua, Y. Uratania, and F. Ishiib
aHiroshima University
bKanazawa University

Megagauss Spectroscopy ofSingle-Walled Carbon Nanotubes
H. Yokoi, E. Kojima, and S. Takeyama
Optical properties of single-walled carbon nanotubes(SWNTs) are governed largely by excitonic states because
the exciton exists stably even at room temperature dueto the one-dimensionality of their structures. It has been
predicted theoretically that the excitonic state is split into
singlet and triplet states due to valley mixing and exchange
at K and K’ points of the Brillouin zone because theelectronic states are degenerate at the points. Among these
excitonic states, only the gerade state of the singlet statesis optically active (“bright”) and the others are opticallyinactive (“dark”). It has been one of the most important
problems in the properties of SWNTs which state locates

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ISSP Activity Report 2007

Fig. 1. Megagauss spectroscopy of excitonic states in single-walledcarbon nanotubes (SWNTs) in a pulsed magnetic field. (a) Waveformof the megagauss field applied in parallel to the alignment of
SWNTs. (b) Contour map of absorbance in an aligned SWNT film as
a function of time and photon energy. The baseline of absorbance
spectra has been removed. Each absorption peak is labeled by SWNT
chirality index (n,m). The absorption peak for (7,5) SWNTs shifts
toward the lower energy side, decreasing its intensity slightly, anda new peak emerges on the higher energy side while that for (6,5)
SWNTs shifts toward the higher energy side, losing its intensity,and a new peak appears on the lower energy side with increasing
magnetic field. The sample was at room temperature.

energetically lower between the singlet “bright” and “dark”
excitonic states.
In order to approach this subject, we have conductedmagneto-absorption measurements of aligned SWNT films
in the visible light region at room temperature under ultrashort pulsed magnetic fields to 200 T using a single-turn coilsystem. We have succeeded to observe changing of absorption peaks originated from the second sub-band excitonin semiconducting SWNTs very clearly with increasing
magnetic field in parallel to the alignment of SWNTs(Fig. 1). The following changes are recognized for SWNTs
with a chiral vector of (6, 5) or (7, 5): The absorption peakobserved at 0 tesla shifts toward the higher energy side
and a new one appears on the lower energy side for the(6, 5) SWNT while the former shifts toward the lower energy
side and the latter appears on the higher energy side forthe (7, 5) SWNT. No modification of absorption spectra has
been detected by the application of magnetic fields perpendicular to the alignment of SWNTs up to 200 T, whichsuggests that the spectral changes mentioned above are
attributed to the Aharonov-Bohm effect.
These experimental results prove that it is the “dark”
excitonic state in (6, 5) SWNT and the “bright” one in (7, 5)
SWNT that situates at the lower energy side in the case of
the singlet splitting of the second sub-band excitonic state.
This configuration is different from that reported in theother magneto-luminescence studies where the “dark” onesituates at lower energies in all of the investigated SWNTs.
Further studies are required to resolve this contradiction.
Authors
H. Yokoia, E. Kojima, S. Takeyama, and N. Minamib

aKumamoto University

bNational Institute of Advanced Industrial Science and Technology

Non-magnetic Ground State andExcitation Gap in New Kagomé
Antiferromagnet Rb2Cu3SnF12
K. Morita, H. Tanaka, and K. Kindo
Two-dimensional S = 1/2 kagomé antiferromagnet (KAF)
is one of the most attractive spin system from the viewpointof synergy effect of quantum fluctuation and geometricalfrustration. Although many theoretical and experimental
studies have been carried out over few decades, thebasic questions such as the ground state properties orthe existence of the finite energy gap above the groundstate are still open. Numerical studies [1,2] reveal that theenergy spectrum of S = 1/2 KAF has the small gap between
the singlet (non-magnetic) ground state to the lowest
triplet (magnetic) state, and that the continuum of thenon-magnetic excitations occupies up to the lowest triplet
state. The experimental studies to test such a unique energy
spectrum for S = 1/2 KAF have not been carried out yet due
to the lack of suitable model substance [3,4].
Our recent studies on the new hexagonal antiferromagnet Rb2Cu3SnF12[5] revealed that this compound has
the slightly deformed kagomé layer with a 2a × 2a enlarged
cell as compared with the proper kagomé layer. Due tothis crystal structure, there exist four kinds of the nearestneighbor exchange interaction J1 ~ J4 between Cu2+ - ions,as depicted in the inset of Fig. 1. Temperature variation of
the magnetic susceptibility shows the steep decrease below
T < 70 K with lowering temperature, which is indicative of
the existence of the energy gap between the non-magnetic
ground state and the magnetic excited state. Using the exact
diagonalization method with J1/kB = 234 K, J2/kB = 211
K, J3/kB = 187 K and J4/kB = 108 K, we have succeededin reproducing the temperature variation of the magnetic
susceptibility except for the low temperature region. To
evaluate the excitation gap directly, we have performed themagnetization measurement, using pulsed high magnetic
field. The magnetization curves for both field directions,
H || c and H ⊥ c, exhibit the bend anomaly at the fieldindicated by the arrows Hc in Fig 4. The energy levelsof ground state and excited triplet state cross at Hc. The
discrepancy of Hc for H || c (~13T) and H ⊥ c (~20T) is causedby the fact that the weak magnetic moment is induced by
the field for H ⊥ c even at the small field (see ref. [5]). This
result shows the first evidence of the non-magnetic groundstate in S=1/2 kagomé antiferromagnet.
References[1] Ch. Waldtmann et al., Eur. Phys. J. B 2, 501 (1998).
[2] M. Mambrini and F. Mila, Eur. Phys. J. B 17, 651 (2000).
[3] M. Rigol and R. R. P. Singh, Phys. Rev. Lett. 98, 207204 (2007).
[4] G. Misguich and P. Sindzingre, Eur. Phys. J. B 59, 305 (2007).
[5] K. Morita et al., J. Phys. Soc. Jpn. 77, 043707 (2008).
Authors
K. Moritaa, T. Onoa, H. Tanakaa, Y. Narumi, and K. Kindo
aDepartment of Physics, Tokyo Institute of Technology

Fig. 1. Magnetization curves of Rb2Cu3SnF12 for the field directions H || c (left axis) and H ⊥ c (right axis) measured at T=1.3K.
Inset shows the network of the nearest-neighbor exchange interactions between magnetic Cu2+-ions (blue circles) in the ab-plane. The
exchange bonds are classified into J1~J4.

ISSP Activity Report 200751

International Conferences and Workshops

Foundations and Applications of the Density Functional Theory (FADFT)

July 19 -August 10, 2007
O. Sugino and Y. Takada

The FADFT consisted of the workshop part (19-31 July and 6-10 August) and the symposium part (1-3 August). In theworkshop two pedagogical lectures were provided everyday and after the lectures significant discussion was done between
the lecturers and junior researchers. On average 20-30 attended the workshop in spite of the hot and humid summer. In
the symposium, thirty three invited talks and twenty three posters presentations were given to survey the frontiers of thisresearch field. 120 attended the symposium.
FADFT was the second of the ISSP international mini workshop/symposium, which is held annually by the theory divisionof ISSP. This time, focus was given to the foundations and the applications of the density functional theory (DFT). FADFT was
co-chaired by Osamu Sugino and Yasutami Takada. It was sponsored by The Institute for Complex Adaptive Matter (I2CAM),
21st Century COE Program "Quantum Extreme Systems and Their Symmetries" of the University of Tokyo, and Grant-in-Aid
for Scientific Research in Priority Areas, "Development of New Quantum Simulators and Quantum Design - A01 Group -" ofMEXT.
The topics selected were(A) Strongly correlated systems- Combined DFT and may-body theories (e.g. LDA+U and GW+DMFT)- Many-body theories beyond DFT (e.g. Quantum Monte Carlo and trans-correlated method)- Efforts to construct new exchange-correlation functionals within/beyond local density approximations (LDA)(B) Excited states- Time-dependent version of DFT (TDDFT)(C) Simulations- New algorithms for supercomputers, including the order-N algorithms- Soft and nano materials- Electronic transport and quantum dynamics of electrons and/or nuclei.
Details on the symposium can be seen in the web site http://www.issp.u-tokyo.ac.jp/public/fadft/. The ppt files and thelecture movies are available on the web site http://www.issp.u-tokyo.ac.jp/public/fadft/program.html, and http://www.issp.
u-tokyo.ac.jp/public/fadft/pict_mov.html, respectively.

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ISSP Activity Report 2007

2nd International Workshop on Protonics and Nano-Interface of Coordination
Chemistry, IWPNICC 2008

March 10-11, 2008
O. Yamamuro and H. Kitagawa

The energy problem is one of the most important scientific problems of the 21st century. In the such social situation,
the role of hydrogen with energy storage and energy conversion functions is becoming more and more significant in theworld. The first purpose of this workshop is to discuss structural and dynamical properties of proton conducting and storage
materials in their bulk state and at interfaces. Another purpose of the workshop is to discuss the development of new proton
conducting and storage systems and their functional nano-layer integrated systems. In the workshop, eight foreign (from six
countries) and nine domestic researchers were invited and gave interesting talks on the above topics. The total number ofparticipants was about sixty.
In the workshop, it was confirmed that the neutron is a powerful prove for hydrogen systems since it has large scatteringcross section and reflectivity for hydrogen atoms and exhibits striking contrast for H and D atoms. It is also suggested
that synchrotron radiation X-ray, NMR, and thermal experiments are also useful and their combination is very effective toinvestigate the physical properties of proton-containing systems. It was remarkable that a variety of new proton conducting
materials and nano-porous materials have been produced recently in the field of coordination chemistry. Theoretical andcomputer simulation works are helpful for designing such new materials and understanding the microscopic electrocatalytic
reactions at electrode interfaces.
This workshop was financially supported by Japan Science and Technology Agency (JST), Core Research for Evolutional
Science and Technology (CREST) Program: Development of the Foundation for Nano-Interface Technology. The management of the workshop was performed by the research stuffs, secretaries, and students of H. Kitagawa laboratory (Kyushu
University), S. Kitagawa laboratory (Kyoto Universty), and Yamamuro laboratory (ISSP).

ISSP Activity Report 2007

53

ISSP Workshops

New Developments in ESR of Strongly Correlated Systems

May 21-23, 2007
M. Oshikawa, M. Hagiwara, H. Kikuchi, S. Miyashita, H. Nojiri, and H. Ohta

Electron Spin Resonance (ESR) is one of the most fundamental experimental probes in condensed matter physics.
However, perhaps its potential has not been fully utilized in research of strongly correlated systems yet. This is primarily
owing to difficulties in the theory of ESR of strongly correlated systems and thus in the interpretation of experimental data.
However, recently, reliable analytical and numerical approaches that include correlation effects have been developed in
one dimension. With the steady advancement of material synthesis and experimental techniques on the other hand, at thisworkshop we had intensive discussions on the present status and future directions of the field.
Thanks to the support from the University of Tokyo COE 21 program “QUESTS” , we could have 8 invited speakers fromabroad. As a consequence, this workshop is organized as an international workshop and all the presentations were given in
English.
Although the subject of the workshop was quite limited, total number of participants over 3 days was as many as 126,
with 26 oral and 9 poster presentations. Lively discussions were held in a relaxed atmosphere.
Among the presentations, there was a report of new experiments which reexamine a 20 years old result. This reminded usthat there are many interesting, long-standing questions in the field.
Details on the workshop can be found in the web page: URL http://oshikawa.issp.u-tokyo.ac.jp/esr/indexj.html

New Opportunities in Materials Science Using High Brilliance Soft X-ray

July 5-6, 2007
A. Kakizaki, T. Miyahara, H.Daimon, M. Oshima, S. Shin and I. Matsuda

The Synchrotron Radiation Research Organization of the University of Tokyo has started to construct a new undulator
beamline at the SPring-8, which will be available in a year or two. The aim of the workshop is to overview the recent
topics and developments in the materials science using synchrotron radiation and to discuss on the scientific opportunities
which will be available at the new beamline at SPring-8. After a brief talk on the new undulator and beamline at SPring-8,
participants including many young scientists discussed on the new scientific opportunities utilizing nano-focusing and/or
pico-second time structure of high brilliance undulator light. They discussed on soft X-ray diffraction experiments to investigate characteristics of hidden surfaces and interface, soft X-ray emission spectroscopy of bio-materials, time-resolved experiments of chemical reactions and nano-magnets, etc. New proposals such as STM imaging and photoelectron diffraction
experiments were also discussed. In the workshop, synchrotron radiation facilities, UVSOR, KEK-PF and SPring-8, reported
on the present status of the light sources and their future plans.

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ISSP Activity Report 2007

Foundations and Applications of the Density Functional Theory (FADFT)

August 1-3 , 2007
O. Sugino and Y. Takada

This ISSP workshop was held as a part of the international workshop of the same title. See the section of “International
Conferences and Workshops”.

Novel Low Temperature Pressure-Induced Phenomena and Current and Possible
Pressure Techniques

October 10-12, 2007
K. Murata, K. Shimizu, H. Takahashi, G. Oomi, and Y. Uwatoko

The purpose of this workshop is to discuss the pressure-induced novel phenomena, superconductivity, magnetic order,
metal-insulator transitions, etc, and to exchange the latest pressure techniques applied to various sort of experimental physics.
In three days, 30 oral and 29 poster presentations were given. Moreover, the number of participants was 154, which is far
beyond the organizer’s expectation and is a proof of high-level interests in these subjects among many researchers. Actually,
during the sessions as well as at the coffee breaks, hot discussions were going on all the time. The workshop concluded withmany outcomes of new phase diagram under pressure as well as possible and/or realizing new pressure techniques, whichhave stimulated not only the experimental but also theoretical physicists.
http://www.issp.u-tokyo.ac.jp/cgi-bin/detail.cgi?c=short_term_society_table::132

Present Status and Prospects of Low Temperature Scanning Tunneling Microscopy

October, 12-13, 2007
H. Fukuyama, N. Nishida, T. Hanaguri, F. Komori, and Y. Hasegawa

Technologies on scanning tunneling microscopy (STM) have been rapidly developed since its invention, and now It is used
for many materials under various conditions. The application has been extended to wide-ranging research fields, and specifically, low-temperature STM has been utilized for researches in surface science, superconductivity, semiconductor materials,
magnetism etc. Although common experimental techniques are used, however, there have been few chances to hear talks ofother fields and share the knowhow since researchers present their results at different societies / sections. In this seminar,
98 researchers and students who perform researches with low temperature STM got together, introduced a state-of-the-art
research in each field mutually and exchanged the technical knowhow through 24 oral and 14 poster presentations andsubsequent discussion. Presentations on surfaces, superconductivity, mesoscopic physics, and local optical response were
provided. The seminar was very fruitful since stimulus discussion promoted mutual understanding among researchers ofvarious fields.

Progress in Computational Physics

November 1-2, 2007
N. Kawashima, N. Furukawa, S. Tsuneyuki, Y. Tomita, and T. Suzuki

While continuous advancement of computer-hardware technology is a strong driving force of modern computational
sciences, recent important developments are largely due to new computational methods and softwares. At the supercomputer
center (SCC) of ISSP, we are accepting approximately 200 new proposals annually from many institutions in Japan, with theaim at developing new algorithms and methods in condensed matter physics. The proposals are classified into three categories: (1) the first-principles calculations of states of matters, (2) strongly-correlated quantum systems, and (3) complex andnon-linear systems. In order to clarify the current state of these fields and motivate further investigations, we invited mostactive researchers, including heavy users of the facilities of SCC, ISSP, and organized the workshop. In particular, we invitedfour researchers to give prenary lectures: Y. Morikawa (Osaka), M. Sasaki (Tohoku), S. Watanabe (Tokyo), and H. Kontani(Nagoya). The first day was focused on the first principles calculations and the second on the strongly-correlated systems
and the complex and non-linear systems. We had totally 80 participants and 44 presentations (30 oral and 14 poster). The
talks and discussions represented the high quality of the activities of the community. In addition, we had a special session for
discussing our possible actions towards the next-generation supercomputer project ( “10-peta-flops project” ) of MEXT, Japan.

ISSP Activity Report 2007

55

Frontiers of Physical Chemistry 2007

November 20-22, 2007
J. Yoshinobu

Since the inception of The Institute for Solid State Physics in 1957, several chemistry-based groups have been engaged
among more than 40 research groups. So far the collaboration between physicists and chemists has given unique outstandingachievements in condensed matter science. In this workshop the present frontiers of physical chemistry and chemical physics
in condensed mater were reviewed. In particular, six subjects were focused: (1) interplay between light and materials, (2)physical properties of nm-scale and low-dimensional materials, (3) dynamics in amorphous and liquid materials, (4) synthesisof exotic materials and their properties, (5) self-organization in soft matter and (6) development and application of newmaterials. In addition, Professor Emeritus Inokuchi gave a special lecture about solid state organic materials in commemoration of his 2007 Kyoto Prize.

Creation and Destruction of Coherence of Light with Short Wavelength and Thosein Materials

November 26-27, 2007
T. Miyahara, M. Aihara, T. Suemoto, and S. Watanabe

In this workshop were discussed various aspects of coherence of light and collective motions in a material interacting withradiation. Creation of higher order coherence is nontrivial in a material system because of the presence of some decohering
mechanisms. Many experimental results were shown to indicate that in most cases the coherent motion of elementary excitations are caused by an incoherent pulses much shorter than the period of oscillation. Also the substantial time was devoted tothe issues about the Berry phase, quantum entanglement, and potential methods to control the phase of motions in a material.
The basic concepts of “energy relaxation” , “phase relaxation” , and “decoherence” were extensively discussed unifying
different terminology used in different groups. Some participants proposed future plans to clarify some unsolved or controversial problems, such as the control of gauge phases or the basic assumptions of quantum mechanics and observation.

On the Experimental Apparatuses in the Outstation Project of the Universityof Tokyo

December 8, 2007
A. Kakizaki, M. Oshima, and S. ShinThe Synchrotron Radiation Laboratory of ISSP has been participating to the Outstation Project of the University of Tokyoand constructing new undulator and beamline at SPring-8. The aim of the workshop is to discuss on the scientific opportunities utilizing high brilliance soft X-ray and to find out a future direction to construct experimental apparatuses at SPring-8. At
the workshop, the difficulties and up-to-date experimental techniques were also discussed to handle with the high brilliancesoft X-ray from undulator, which inevitably accompany with high heat flux more than 100w/mm2. Six proposals of the
new apparatuses were presented and discussed. The discussion was summarized to suggest that the construction would bestated with the experimental apparatuses for soft X-ray emission spectroscopy of bio-materials, time-resolved experiments ofchemical reactions and nano-magnets and photoemission experiments on nana-structure materials. They also recommended
a post-focusing mirror system so that many apparatuses designed and constructed for experiments using high brilliance soft
X-ray could be connected.

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ISSP Activity Report 2007

Hydrogen and Water in Condensed MatterFebruary 4, 2008
J. Yoshinobu

Hydrogen and water are ubiquitous in the universe and on the earth, but their states of existence are still under intensive
research. In addition, hydrogen and water play important roles in materials, including proton transfer, hydrogen absorption,
catalytic reactions on surfaces, electrochemistry, ice, gel, etc. Recent activities in this field have been growing very rapidly
using many different techniques; neutron scattering, synchrotron radiation, ultra-fast lasers as well as first-principles calculations. In this workshop, we reviewed and discussed the present status of hydrogen and water in condensed matter physics
and chemistry.

ISSP Activity Report 200757