Highlights of Joint Research

Synchrotron Radiation Laboratory
The Synchrotron Radiation Laboratory (SRL) wasestablished in 1975 as a research group dedicating to study
solid state physics using synchrotron radiation. Since 1980s,
SRL has been promoting theSuper-SOR
project for
constructing a new synchrotron radiation facility with a third
generation light source dedicated to the sciences in vacuum
ultraviolet and soft X-ray (VSX) regions. In 1985, 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 andtwo beamlines, BL-19A and BL-19B for spin-resolved
photoelectron spectroscopy and soft X-ray emission
spectroscopy experiments using undulator radiation. They
are fully opened to outside users for experiments using highbrilliant synchrotron radiation from the undulator. The
operation time of these beamlines are about 5000 hours andthe number of users 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 new
accelerator related technology in collaboration with other SR
facilities, which play essential roles in the Super-SOR
project. The spectroscopy group not only serves users at the
Tsukuba branch with technical supports and advices, butalso carry out their own research works on advanced solidstate spectroscopy as well as instrumentation for the super
SOR project.
The scientific highlights achieved in 2004 at the Tsukuba
branch are found in the studies of magnetic properties ofthin films. One is the study of electronic structures ofFe thin films grown on Rh(100) surface by spin-resolved
photoemission (J. Phys. Soc. Jpn. 73, 2250 (2004)). It was
found that the Fe films not thicker than 3 ML are magnetically dead on the Rh(100) surface due to a large strain at
the Fe/ Rh(100) interface, which was supported by MCD
experiments and total energy calculation of Fe films with fct
structure. The other is the study of Fe(wedge)/NiO(100)system by PEEM experiments (J. Phys. Soc. Jpn. 73, 2932
(2004)). By comparing antiferromagnetic domain imagesof NiO(100) observed at Ni L2 and O K edges in aFe(wedge)/NiO(100) system, they have successfully distinguished two types of domains, namely T-domain originatingfrom the crystallographic twinning effects due to the rhombohedral contraction and S (spin) -domain.
The accelerator group demonstrated that the emittance ofthe electron beam in the Super-SOR storage ring can be
improved to be 3 nmrad, which will be smaller than those of
the existing VUV and soft X-ray SR sources. They also
made progress with the hardware design of the ring and the28

ISSP Activity Report 2004

booster synchrotron. In the R&D of the Super-SOR project,they developed a new beam profile monitor using an X-ray
imaging optics with two Fresnel zone plates and succeeded
in measuring the beam size less than 6 microns and theradiation damping times with and without damping wigglers
in the KEK accelerator test facility. The new orbit correction
method, the eigenvector method with constraints, wasexperimentally studied by using the PF ring as well as the
PF-AR and its excellent correction performance was demonstrated by this study.

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 ResearchInstitute in Tokai. 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 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 physics,
researches are mostly carried out by using the small angle
neutron scattering (SANS-U) and/or neutron spin echo(NSE) instruments. The upgraded time-of-flight (TOF)
inelastic scattering spectrometer is also available from May
2005.
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
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.
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.
The NSL also operates the U.S.-Japan cooperative programon neutron scattering, providing further research opportunities to material scientists who wish to utilize the neutron
scattering technique for their research interests.
The details of individual studies in the JFY2004 arereported in the NSL-ISSP Activity Report vol. 12.

Supercomputer Center
The supercomputer system in the Supercomputer Centerof the Institute (SCC-ISSP) is placed at the service ofgeneral researchers of condensed matter physics throughthe User Program conducted by the Materials Design andCharacterization Laboratory (MDCL). One of its aims is toselectively promote and support huge computations.
In fiscal year 2004, which was the last one of the fiveyear rental period of the system, the SCC-ISSP main system
consisted of two supercomputers: Hitachi SR8000/60, a
distributed-memory-type parallel supercomputer with 640GB
memory in total and 12x60GFlops peak performance (called
System-A), and SGI Origin 2800/384, a massively parallel
supercomputer with 192GB memory and 0.8x384GFlops
peak performance (called System-B). Now in fiscal year
2005 they are replaced by Hitachi SR11000/48 model J1
with 2.8TB memory and 5.8TFlops peak performance, andby SGI Altix3700/1280 with 1.3TB memory and 7.7TFlops
peak performance, respectively.

A project(s) can be proposed by any staff in universities
or public research institutes in Japan. The projects proposed
are judged by the Steering Committee of the SCC-ISSP,
under which the Supercomputer Project Advisory Committee
is formed to review proposals. In fiscal year 2004 totally 151
projects were approved. The total points applied andapproved are listed on Table 1 below.
The research projects are roughly classified into the following three (the number of projects approved):
First-Principles Calculation of Materials Properties (55)
Strongly Correlated Quantum Systems (59)
Cooperative Phenomena in Complex, Macroscopic Systems (37)
All the three involve both methodology of computationand its applications. The results of the projects are reported
in 'Activity Report 2004' of the SCC-ISSP. In the report thefollowing four invited articles are included:"Realization of a Computer Simulation Environment
based on ITBL and Large Scale LDA and GW
Calculations Performed on this Platform", byY. Kawazoe, M. Sluiter, K. Ichinoseki, K. Ohno, S. Ishii,
R. Hayashi, Y. Inoguchi, H. Adachi, H. Yamaguchi, andC. Kitagawa,"Structural Properties of Solid Oxygen: Density
Functional Study", by T. Oda,
"Quantum Number Projection and Path Integral
Renormalization Group Method", by T. Mizusaki and M.
Imada,"New Type of Universality on Ne'el Temperaturesof Quasi-Low-Dimensional Antiferromagnets", by C.
Yasuda, S. Todo, K. Hukushima, F. Alet, M. Keller, M.
Troyer, and H. Takayama.
The first article above is the report of a special project, bywhich 4 nodes of system-A were exclusively used in whole
fiscal year 2004 for testing the method for the parallel usageof remote supercomputers that its authors are developing.
The brief report of the fourth article is reported in this volume as a highlight of the joint-use researches.

Table 1: Research projects approved in 2004========================================================================Class Max.Point Application# of Proj.
Total points
AppliedApproved
Sys-A
Sys-B
Sys-A
Sys-B
-------------------------------------------------------------------------------------------------------------------------A
100k
any time
4
200K
200K
200K
200K
B
2M
twice a year
48
67.1M
23.65M
66.1M
23.45M
C
20M
twice a year
931044.5M
542.2M
954.3M
508.7MDnone
any time
6
37M
106M
35M
103M
========================================================================For System-A 1 K point corresponds to charge for CPU time of about 0.43 hours by one processing
element, while the corresponding figure is 2.32 hours for System-B.

ISSP Activity Report 200429

Exploration of Ultimately Dense Phaseof Dioxide under High Pressure
N. Funamori and T. Yagi
Materials transform to denser phases with increasingpressure. The densest structure of dioxides reported so far is
the PbCl2 type in which each cation is surrounded by 9 oxygens (9-fold coordinated). Many dioxides with large cations
are known to have the PbCl2 structure under high pressure,but any phase transformation to the structure with a coordination number of 10 or higher, namely the post-PbCl2 structure, has not been reported. The purpose of this study is to
explore the post-PbCl2 transformation of dioxides. Since leadis in the same group of carbon and silicon and PbO2 isknown to have the PbCl2 structure under high pressure [1],CO2 and SiO2, which are important compounds in Earth &Planetary Physics, may have the PbCl2 and/or the post-PbCl2
structure at ultimately high pressures (for example, inside thegiant planets). At present, pressures above 100~200 GPa are
not easy to achieve in static-compression experiments. Since
there is an inverse correlation between cation radius andtransition pressure, it is better to choose a dioxide with alarger cation to explore the post-PbCl2 transformation in alimited pressure range. We chose TeO2whose cation radius islarger than those of dioxides reported to have the PbCl2
structure, such as CeO2, TiO2, ZrO2, HfO2, and PbO2 [e.g.1 - 3].
In this study, phase transformations of TeO2 have been
investigated up to 150 GPa using the diamond-anvil cell.
TeO2 (paratellurite, 6-fold coordinated) powder was loaded
in a rhenium gasket without pressure medium and compressed to a target pressure and then heated using Nd:YAG
laser to anneal deviatoric stresses and/or to overcome kinetic
barriers to transformations. The sample itself absorbed thelaser beam. Angle-dispersive synchrotron X-ray diffraction

3.0

Ar (113)411/022
Ar (220)
031
230
420

212

Ar (200)002

400/221

Ar (111)

2.5

2.0

122
202/240
400

031
221
131
230
002/040
320/140
311
231

1.7

1.475
1.435
1.400
1.376

1.585

1.705

1.803

1.979
1.886

2.534
2.830
2.644
2.467
2.420
2.373
2.279 †
2.195

3.171

2.943

(c) 130 GPa

4.0

TeO2

1.5

d-value (Å)
Fig. 1. X-ray diffraction patterns of TeO2 for (a) the paratellurite phaseat 12.3 GPa, (b) the PbCl2 phase at 53 GPa, and (c) the post-PbCl2
phase at 130 GPa. The diffraction lines of the paratellurite phase and
the PbCl2 phase are labeled hkl Miller indices, assuming P212121 andPnam symmetries, respectively. Experiments below 20 GPa were carried out with argon pressure medium without laser heating (see text).
The diffraction lines of argon are labeled Ar(hkl). Because the structureof the post-PbCl2 phase has not been determined yet, the diffractionlines in (c) are labeled d-values in Å, instead of Miller indices. The diffraction lines with an asterisk (*) and a dagger ( @ ) may be impurity
lines.

30

References[1] J. Haines, J. M. Leger, and O. Schulte, J. Phys.: Condens. Matter 8,1631 (1996).
[2] S. J. Duclos et al., Phys. Rev. B 38, 7755 (1988).
[3] N. A. Dubrovinskaia et al., High Pressure Research 22, 391 (2002).
[4] A. Jayaraman and G. A. Kourouklis, Pramana-J. Phys. 36, 133(1991).
[5] J. M. Leger et al., Phys. Rev. B 52, 13247 (1995).
[6] J. Haines, J. M. Leger, and O. Schulte, Phys. Rev. B 57, 7551
(1998).
Authors
N. Funamoria, T. Satoa, T. Yagi, and N. Miyajima
a Department of Earth and Planetary Science, University of Tokyo

121
201/220
130
211

020

011
120
200

111

(b) 53 GPa*

Intensity

101

020

201

011

210/111(a) 12.3 GPa

experiments were carried out using an imaging-plate detector
at BL-13A and BL-18C of the Photon Factory (Tsukuba,
Japan). All measurements were conducted at room temperature after heating.
Fig. 1 shows typical X-ray diffraction patterns for threephases of TeO2 observed in this study. Our X-ray diffraction
measurements confirm the transformation from the paratellurite phase (Fig. 1(a)) to the PbCl2 phase (Fig. 1(b)) that has
been inferred from Raman scattering measurements [4] atpressures of 20~30 GPa. A fit of measured pressure-volumedata of the PbCl2 phase to the second-order BirchMurnaghan equation of state gave the zero-pressure bulk
modulus K0 = 115 !17 GPa (and the zero-pressure molar
volume V0 = 23.3 !0.6 cm3/mol). This bulk modulus is as
small as (or smaller than) about a half of those of other
PbCl2-structured dioxides [e.g.1 - 3], implying that the PbCl2
structure of TeO2 is more sensitive to pressure than theothers. This supports our speculation that TeO2 may transform to a post-PbCl2 phase at relatively low pressures.
Indeed, a further transformation to a post-PbCl2 phase(Fig. 1 (c)) has been observed for the first time in dioxides atpressures of about 80~100 GPa. The X-ray diffraction
pattern of the post-PbCl2 phase of TeO2, however, could not
be explained by assuming the post-PbCl2 structures reported
in dihalides such as the Co2Si and Ni2In structures [5, 6], andthe nature of this phase has not been clarified yet. The PbCl2
phase of TeO2 contracted rather isotropically with increasingpressure similar to other dioxides [1, 3], in marked contrast
with the anisotropic contraction of the PbCl2 phases ofdihalides [5, 6]. These results suggest that the mechanism of
the post-PbCl2 phase transformation in dioxides may bedifferent from that in dihalides.

ISSP Activity Report 2004

Organic Semiconductor with Divalent
BEDT-TTF Molecules
H. Ito and H. Tajima
The BEDT-TTF [bis(ethylenedithio)tetrathiafulvalene]
molecule has been widely used as a constituent of conducting and superconducting cation-radical salts. It is widelybelieved that in order to realize electrical conduction in
BEDT-TTF salts, incomplete charge transfer between
BEDT-TTF and appropriate acceptors is important so as tohave an intermediately-filled conduction band comprisedof overlapping highest-occupied molecular orbitals (HOMO)of the BEDT-TTF molecules. Recently, Kanehama et al.
reported the rather high conductivity of 10-2 S/cm in(BEDT-TTF)Cu2Br4. Figure 1 shows the temperaturedependence of conductivity. The conductivity shows thermally activated behavior with activation energy of 0.16 eV

Fig. 1. The temperature dependence of the resistivity of(BEDT-TTF)Cu2Br4. Inset: the chain structure of BEDT-TTF2+ andCu2Br42-.

below 170 K and 0.09 eV above 170 K. This salt attracts
interest in the sense that the valence state of BEDT-TTF
is considered to be 2+, because Cu ions are monovalent
found by ESR measurements. There are only few
preceding examples of salts with divalent BEDT-TTF,(BEDT-TTF)(BF4)2 and (BEDT-TTF)(ClO4)2, and more
recently (BEDT-TTF)[Fe(CN)4(CO)2], but they are all
insulators with conductivities less than 10-5 S/cm. The goodelectrical conductivity of (BEDT-TTF)Cu2Br4 contradicts tothe closed-shell state of BEDT-TTF with no electrons in the
HOMO band. It is noted that the S atoms of the BEDT-TTF
molecules are coordinated directly to the Cu atoms of theanion clusters with a bond length of 2.38 Å, forming a chain
structure along the c-axis as shown in the inset of Fig.1.
Figure 2 shows the Raman spectrum under He-Ne Laser
excitation, polarized perpendicular to the c-axis at room temperature. Among the observed Raman signals, v2, v3, v5, v6,
v7, and v9 can be assigned to major ag mode molecular vibrations of BEDT-TTF. The ag mode molecular vibrations are
known to be sensitive to the charge concentration on HOMO
of BEDT-TTF. In the present salt, these are observed at1383, 1310, 1298, 943, 916, and 530 cm-1, respectively.
These Raman shifts are in good agreement with the results
for the divalent salt of (BEDT-TTF)(ClO4)2 [2], indicatingthat the present salt is composed of divalent BEDT-TTF
molecules. The Raman spectrum is almost unchanged withtemperature down to 20 K, indicating that the valence stateof BEDT-TTF remains divalent down to 20 K. The opticalFig. 2. Raman spectrum at room temperature of a single crystal of(BEDT-TTF)Cu2Br4 under He-Ne laser excitation, polarized
perpendicular to the c-axis.

conductivity of (BEDT-TTF)Cu2Br4 exhibits a semiconducting behavior with the electronic gap of 0.7 eV, which contradicts to the low activation energy found by the conductivity
measurement. This implies that (BEDT-TTF)Cu2Br4 is an
extrinsic semiconductor.
In order to obtain insights into the origin of the charge
carriers, the Hall coefficient and π-electron ESR measurements were performed [3]. By the Hall coefficient measurement, charge carriers are electron-like and their concentration is rather low of 4 !2 #1019 /mol at room temperature.
The carrier concentration increases exponentially with temperature with an activation energy of 0.17 eV below 170 K
and 0.12 eV above 170 K. The Hall mobility is as high as
2 cm2/Vs, supporting the high conductivity of the salt. The
carrier concentration at room temperature is one order ofmagnitude lower than the concentration of Curie spin from
impurity sites. The fine structure of the ESR signal of Curie
spins smears away above 100 K, as caused by exchangeinteraction mediated via conduction electrons. These results
indicate that charge carriers localized at low temperatures arethermally activated to the conduction band at high temperatures to contribute to the conduction. The possible origins of
the charge carriers are impurity sites of the different crystal
phases of (BEDT-TTF)2[Cu4Br6(BEDT-TTF)] in the matrix.
References[1] R. Kanahama et al., Inorg. Chem. 42, 7173 (2003).
[2] H. H. Wang et al., Mol. Cryst. Liq. Cryst. 284, 211 (1996).
[3] H. Ito et al., Phys. Rev. B 71, 085202 (2005).
Authors
H. Itoa, Y. Yokochia, H. Tanakaa, S. Kurodaa, R. Kanehamab,
M. Umemiyab, H. Miyasakab, K-I. Sugiurab, M. Yamashitab,
H. Tajima, and J. Yamauraa Department of Applied Physics, Nagoya University
b Department of Chemistry, Tokyo Metropolitan University and CREST

Novel Technique for Thermal
Conductivity Measurements for Organic
Materials and the Thermal Conductivityof (DMe-DCNQI)2Li1-xCux (0 E x E 1)
K. Torizuka and H. Tajima
Organic molecular conductors have recently attracted theinterest of many researchers in condensed matter physics. In
order to explore the properties of organic compounds, so far
electrical conductivity, susceptibility and NMR measurements have been mainly carried out. Other measuring techniques have been little used for organic samples. This isbecause organic materials are in general so small and fragilethat it is very difficult to manipulate. Many researchers have
today expected that a new technique should be put into
practice in the research field of organic materials. With suchsituation, we paid our attention to the thermal conductivity
measurement. We have developed a new technique to measure the heat conduction for organic samples.
What is new in our technique is the installation of two
heaters and three thermometers unlike the conventional
technique. Our method takes into account the heat leakthrough electrical leads. We apply a heat pulse twice. By first
application of the heat Q, the heat flows both through thesample and through the leads, i.e.,
Q = (∆T)κ1+(∆T0)κ2
where κ1 and κ2 are thermal conductivities of the sample and

ISSP Activity Report 200431

height decreases with decreasing Cu concentration x, andfinally vanishes in the x=0 sample. We have proposed thephonon scattering mechanism that the spin Peierls lattice
distortion may suppress the phonon propagation. We havediscussed the effect of the spin Peierls lattice distortion on
the phonon propagation for the first time [2].
We have measured the thermal conductivity of x=1 and
x=0.75 samples as well, which are metals and are classified
into a different class from samples of 0 Ex E0.14. Physicalinterpretations on experimental data are now in progress.
References[1] K. Torizuka et al., Rev. Sci. Instrum. 76, 033908 (2005).
[2] K. Torizuka et al., Phys. Rev. B 71, 193101 (2005).
Authors
K. Torizuka, H. Tajima, T. Yamamotoaa Institute for Molecular Science

Giant Nonlinear Conduction in the
Organic Salt θ-(BEDT-TTF)2CsZn(SCN)4Fig. 1. Actual experimental setup.

the leads, respectively, and ∆T and ∆T0 are temperature
differences across the sample and across the leads, respectively. Then we excite the sub-heater that is installed ona copper stage to which all electrical leads coming fromthermometers and the main heater are thermally anchored,
and thus we can change the copper stage temperatureslightly( E0.8 K). Under this condition, we apply second heat
Q, which again flows both through the sample and throughthe leads, i.e.,
Q = (∆T')κ1+(∆T0')κ2
where the temperature differences across the sample andacross the leads are varied to ∆T' and ∆T0', respectively. Bysolving these two equations, we can obtain the thermal
conductivities κ1 and κ1. This is the basic concept of ourmeasurements. The actual setup is sketched in Fig. 1. We canmeasure the heat conduction over a wide range oftemperatures (4 ET E250K). The resolution of our method is~1.0 #10-6 W/K, that is very sensitive. The details of ourapparatus have been described elsewhere [1].
The temperature dependences of the thermal conductivityof spin Peierls organic materials (DMe-DCNQI)2Li1-xCux(x=0, 0.08, and 0.14) are depicted in Fig. 2. We observed thephonon contribution in the whole range measured. A phonon
peak can be seen near 20 K. This peak denotes a crossover
between the phonon mean free path that diverges as T-2 andthe phonon specific heat that decreases as T3. The peakFig. 2. The thermal conductivity(DMe-DCNQI)2Li1-xCux (0 E x E 0.14).

32

vs.

temperature

ISSP Activity Report 2004

of

the

I. Terasaki and H. Mori
Very recently, "intrinsically inhomogeneous" states haveattracted a keen interest in strongly-correlated electron systems. A prime example is high-temperature superconductors,
in which nano-size domains of the superconducting-gap andpseudo-gap phases coexist in the CuO2 plane [1]. Anotherexample is perovskite manganites, in which percolation pathsof the ferromagnetic metal phase give rise to colossal magnetoresistance effects [2]. These nano-scale inhomogeneities
are driven by competing orders, not by imperfections of thecrystal, hence the name "intrinsic inhomogeneity" [3].
We have discovered giant nonlinear conduction in theorganic salt θ -(BEDT-TTF)2CsZn(SCN)4, which can be
ascribed to a brand-new phenomenon of intrinsically inhomogeneous states [4]. This salt is a layered material composed of conducting BEDT-TTF layers and insulating

Fig. 1. The voltage-current characteristics of the organic salt
θ -(BEDT-TTF)2CsZn(SCN)4. The current is applied along the c-axis
direction (along the conducting BEDT-TTF plane). Note thatnegative derivative resistance like a thyristor appears below 6 K for
1 mA < I < 10 mA.

CsZn(SCN)4 layers alternately stacked along the b axis. The
Greek letter θ specifies a packing pattern of BEDT-TTF molecules in the conducting layer, representing a "triangular lattice" Because of charge frustration on the triangular lattice,
two kinds of charge order compete at low temperatures. They
are eventually frozen as nano-size domains without longrange order. In fact, no jump or cusp is detected in either the
specific heat or the susceptibility.
Figure 1 shows the voltage-current (V-I) characteristicsof the present salt. The current is applied along thec-axis direction (along the conducting BEDT-TTF plane).
The V-I characteristics are highly nonlinear below 10 K. In
particular, negative derivative resistance appears below 6 K
for 1 mA < I < 10 mA, behavior normally associated withthyristor devices. In this sense, we may call the θ -salt an"organic thyristor".
The most important finding is that the nonlinear conduction is realized without any thermodynamic transitions. This
is in stark contrast to a charge-density-wave (CDW) conductor, in which the conduction is ohmic above the transition
temperature Tc but becomes highly nonlinear (sliding motionof CDW) below Tc. The CDW transition with long rangeorder is indispensable in this case.
We have ascribed the data in Fig. 1 to melting of thecharge-order domains by an external current. This is a
non-equilibrium thermodynamic phenomenon in which
ordered phase domains are melted by an external steadyflow. On a cold wintry day, we often see ice on a pond andwater flowing in a river. The present result is a manifestationof such phenomena in a sea of conduction electrons.
References[1] K. M. Lang et al., Nature 415, 412 (2002) .
[2] M. Uehara et al., Nature 399, 560 (1999).
[3] J. Burgy et al., Phys. Rev. Lett. 87, 277202 (2001).
[4] K. Inagaki, I. Terasaki, H. Mori and T. Mori, J. Phys. Soc. Jpn. 73,
3364 (2004) and references therein.
Authors
I. Terasakia, M. Abdel-Jawadb, N. E. Husseyb, F. Sawanoa, H. Mori,
and T. Morica Waseda Universityb University of Bristol
c Tokyo Institute of Technology

Exact Calculation of Correlation Functions
for the Spin-1/2 Anti-Ferromagnetic
Heisenberg Chain
anti-ferromagnetic

spin-1/2

Heisenberg

chain

L

H = J !S j : S j +1
j=1

S j : S j + 4 = 1 - 16ln2 + 145 g (3) - 162 g (3)ln2
4
2
879
875
2
g (3) g (5) + 1450g (5)ln2
4
4- 825 g (3) g (5) - 5625 g (5)2 + 9555 g (7)
16
16
64
5145
19845
g (7)ln2 +g (3) g (7)432Thus nowadays, it is no more a dream to obtain the exact
analytic expressions for the correlation functions for the antiferromagnetic Heisenberg chain. In fact, more and more new
results are being reported successively [6].
References[1] M. Takahashi, Thermodynamics of One-Dimensional Solvable
Models (Cambridge University Press, Cambridge 1999).
[2] K. Sakai, M. Shiroishi, Y. Nishiyama, and M. Takahashi, Phys.
Rev. E 67, 065101 (2003).
[3] H. E. Boos and V. E. Korepin, J. Phys. A: Math. Gen. 34, 5311
(2001).
[4] H. E. Boos, V. E. Korepin, and F. A. Smirnov, Nucl. Phys. B 658,
417 (2003).
[5] H. E. Boos, M. Shiroishi, and M. Takahashi, Nucl. Phys. B 712,
573 (2005).
[6] J. Sato and M. Shiroishi, J. Phys. A: Math. Gen. 38, L405. (2005).
Authors

H. E. Boosa, M. Shiroishi, and M. Takahashia University of Wuppertal

Magnetic "Ice-Order" in Honeycomb
Nano-Network of Permalloy Wire
H. Miyajima and Y. Iye

H. E. Boos and M. Takahashi
The

Here g (s) is the Riemann zeta function. It was quite recently
that Sakai et al [2] succeeded in calculating the third-neighbor correlator
S j : S j + 3 = 1 - 9 ln 2 + 37 g (3) - 14g (3) ln 2
4
2
9
125
2
- g (3) g (5) + 25g (5) ln 2
2
8
by evaluating the relevant multiple integral formulas using
the method in [3]. More recently a different but more
efficient way to calculate the correlation functions has
been devised in [4] based on the quantum KnizhnikZamolodchikov equations. We have generalized this new
method further and succeeded in calculating all the correlation functions among five lattice sites. In particular, thefourth-neighbor correlator was obtained as [5](J > 0) is one of the most fundamental

models in the study of quantum magnetism in low dimensions. The eigenvalues and the eigenfunctions of the systemespecially for the ground state were obtained by Bethe
ansatz, which allowed us to calculate many physicalquantities exactly [1]. However, as for the exact analytic
evaluation of the correlation functions, it has not beensolved fully yet, although there are rapid developments
recently. For example, the exact results for the two-point
spin-spin correlators in the ground state in the thermodynamic limit (L " 3) had been known only for the nearestneighbor S j : S j + 1 = 1 4 - ln2 and the second-neighbor
S j : S j + 2 = 1 4 - 4ln2 + 9 4 g (3) ones for a long time [1].

Control of magnetic domain structure is one of the key
ingredients of the study of magnetic nanostructures withpossible application to future data storage devices and spintronic functionality devices. In this work we have studied themagnetic domain configuration and magnetization process inmagnetic nanostructure with geometrical frustration.
Samples of permalloy (Ni81Fe19) wire network withhoneycomb pattern were fabricated by electron-beam lithography followed by electron-beam evaporation and lift-off
process (Fig.1(a)). The magnetic domain pattern of the
network was investigated by a magnetic force microscope(MFM) observation. Magnteoresistance measurements were
performed in a vector magnet system which enabled us tocontrol the in-plane and out-of-plane components of appliedmagnetic field and also the azimuthal angle of the in-plane
field with respect to the probe current.

ISSP Activity Report 2004

33

Fig.1. (a) Scanning electron micrograph of the permalloy honeycomb
network. (b) Magnetic force microscope (MFM) image of the network,
the bright and dark spots at the vertices reflect the stray field emanating
there.

Figure 1(b) shows the MFM image of the network in aremanent state after application of µ0H⊥=1T. The individual
wire segments are expected to be of single domain with magnetization oriented parallel to the wire due to the shapeanisotropy. The bright and dark spots seen at the vertices
testify that this is indeed the case, and that the domain
configuration of the three wire segments differs from vertex
to vertex. In general, there are four possible configurations,i.e. "three-in", "two-in/one-out", "one-in/two-out", and"three-out". However, it was found that all the bright anddark spots are roughly equal in magnitude, which means that
only two of the above four possible configurations are present in reality. The fact that some of the wire segments havethe same bright (or dark) spots on both ends, rules out thepossibility of these spots being "three-in" or "three-out".
Thus the configuration at each vertex must be either"two-in/one-out" or "one-in/two-out". Since there are threepossible choices of the "one" for each of these configurations, the total number of possible configurations at eachvertex is six. This is an analog of the so-called "ice-rule", andthis leads to a large degeneracy in the magnetization configuration of the total system. The problem can be mapped onto
an Ising spin model on a kagome lattice.
The magnetization process of the honeycomb network
was traced by magnetoresistance measurements. Figure 2(a)shows the magnetoresistance as a function of the parallel
field H|| oriented to θ =75°
with respect to the direction of theprobe current, in the absence of perpendicular field. The
abrupt jumps in resistance correspond to rapid reversal of theFig.2. (a) Magnetoresistance trace as a function of the parallel field H||
in the absence of perpendicular field, showing two jumps. (b) Similar
trace with µ0H⊥=0.4T showing three jumps.

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ISSP Activity Report 2004

wire segment magnetization. In this case as well as in theabsence of the perpendicular field, only two abrupt jumps
occur in the course of the H||-sweep, despite that there exist
three non-equivalent orientations of the wire segments withrespect to H||. This behavior suggests that the ice-rule
dictates the magnetization process and the remanent state.
Namely, in this case, the magnetization reversal of the threeinequivalent wire segments are not independent fromeach other because of the prohibition of the "three-in" and"three-out" configurations.
Figure 2(b) shows a similar trace taken while a slightly
stronger perpendicular field (µ0H⊥= 0.4T) is applied. In thiscase, three discontinuities are observed, indicating that theconstraint by the ice-rule is lifted. In the presence of perpendicular magnetic field, the magnetic energy at the vertices
are reduced, so that the energy differences between the"three-in" or "three-out" and the other two configurations
becomes smaller, making the former two configurations
accessible.
Reference[1] M. Tanaka, E. Saitoh, H. Miyajima, T. Yamaoka, and Y. Iye,
J. Appl. Phys. 97, 10J710 (2005).
Authors
M.Tanakaa, E.Saitoha, H.Miyajimaa, T.Yamaokab, and Y.Iyea Department of Physics, Keio University
b SII NanoTechnology Inc.

STM and AFM; Which is better for
Surface Structural Analysis?
Non-contact AFM Studies on
Ge/Si(105) Surface
Y. Hasegawa and T. Sakurai
Scanning tunneling microscopy (STM) has been utilized
to determine surface atomic structure with its atomicallyFig. 1. Filled-state STM, empty-state STM and nc-AFM images of theGe(105)-(1 #2) surface and its structural model. The (1 # 2) unit cell
(1.39 nm # 1.08 nm) is depicted at an identical position in each figure.

Authors
T. Eguchi, Y. Fujikawaa, K. Akiyama, T. An, M. Ono, T. Hashimotob,
Y. Morikawac, K. Terakurad, T. Sakuraia, M.G. Lagallye, and
Y. Hasegawa,a Institute for Materials Research, Tohoku University
b Research Institute for Computational Sciences, AISTc The Institute of Scientificand Industrial Research, Osaka University
d Creative Research Initiative, Hokkaido University
e University of Wisconsin-Madison

Dynamics of Super Spin and Mass
Currents in 3He-A1
H. Kojima and H. Ishimoto

Fig. 2. Electrostatic potential mapping (a) and profile (b) taken on the
Ge/Si(105) surface.

resolved images. Probing surface electronic states near the
Fermi energy, STM images, however, do not necessarily represent the atomic structure of surfaces. It has been naively
believed that atomic force microscopy (AFM) provides us
with surface topographic images without being disturbed by
the electronic states. In order to demonstrate the possibly
unique property of AFM, we performed non-contact AFM(nc-AFM) studies on the Ge/Si(105) surface [1], which is afacet plane of the nano-size "hut" clusters formed on
Ge-deposited Si(001) surface.
As presented in Fig. 1, neither filled-state images nor
empty-state images of STM shows all surface atoms. This isdue to the fact that the atoms observed in the filled-state
image, called normal dimer atoms and colored yellow in the
structural model, have dangling bond states below the Fermi
energy (EF) while the atoms in the empty-state image, called
rebonded atoms and colored orange in the model, have states
above EF [2]. On the other hand, in a nc-AFM image all surface atoms having a dangling bond are clearly observed,
directly representing an atomic structure of the surface.
Atomically resolved AFM images are realized by detecting a covalent bonding between the surface and tip apex
atoms [3]. When dangling bonds are tilted from the surface
normal, thus, the observed atom position should be shiftedfrom its core in AFM images. The slight difference in theatomic positions between the model and AFM image is
explained with the tilted dangling bonds.
Electronic information can also be obtained in AFM byusing a Kelvin-probe method. From atomically resolved potential profile obtained with Kelvin-probe force microscopy, chargetransfer among the dangling bond states is directly observed.
These results clearly demonstrate that highly-resolved ncAFM with the Kelvin-probe method is an ideal tool for
analysis of atomic structures and electronic properties of surfaces, surpassing STM.
References[1] T. Eguchi, Y. Fujikawa, K. Akiyama, T. An, M. Ono,
T. Hashimoto, Y. Morikawa, K. Terakura, T. Sakurai, M.G. Lagally,
and Y. Hasegawa, Phys. Rev. Lett. 93, 266102 (2004).
[2] Y. Fujikawa et al., Phys. Rev. Lett. 88, 176101 (2002).
[3] T. Eguchi and Y. Hasegawa, Phys. Rev. Lett. 89, 256105 (2002).

When liquid 3He is cooled in a magnetic field to low
enough temperatures, the normal liquid first makes a transition 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 and established by
Kojima. Nevertheless earlier experiments on this interesting
magnetically driven superflow have uncovered puzzling
problems. One is the origin of the induced fountain pressure
relaxation and the other is the origin of the observed abruptchange in the relaxation time near the middle of the A1
phase. To clarify these, the magnetic fountain detector
should be placed in the sample cell containing only A1 phaseliquid without the interfaces with any other superfluidand normal phase. To realize such conditions, the ISSP
nuclear refrigerator with a large experimental space anda high magnetic field capability up to 15 T has been
assigned as a US-Japan (NSF-JSPS) joint scientific program.
Experimentally a pulsed magnetic field gradient was applied
across a superleak between two chambers, and then theaccompanied pressure increase and relaxation was measured

Fig. 1. Relaxation time as a function of reduced temperature( t= ( Tc1 - T )/( Tc1 - Tc2 ) ).

ISSP Activity Report 200435

with a sensitive differential pressure sensor over the entire
magnetic field and pressure region of the A1 phase.
Figure 1 is one of the typical results. Relaxation time (τ) is
given as a function of normalized reduced temperature( t= ( Tc1 - T )/( Tc1 - Tc2 ) ) at 5 and 8 T. No abrupt change
is observed near t~0.5, confirming a Grabinski's hypothesison the effect from the interfacial boundary against the A2 andthe normal phase. As for the pressure dependence, there is a
substantial decrease in τ at t=0.5 with increasing the pressure
from zero to 30 bar. No or small magnetic field dependence
has also observed above 1.5 T, compared with a linear
increase in the low field region below 1.0 T. To understandthe observed phenomena and to realize a "spin filter" experiment in the A1 phase, further endeavor including the regulation of the sample cell wall is now under way.
References[1] R. Masutomi, H. Kojima, K. Kimura, A. Yamaguchi, and
H. Ishimoto, J. Low Temp. Phys. 138, 789 (2005).
Authors
H.Kojimaa, R.Masutomia, K.Kimura, S.Kobayashi, A.Yamaguchi, and
H.Ishimotoa Rutgers University, Picataway, NJ 08854, U.S.A.

Aharonov-Bohm Effect in Aligned
Single-walled Carbon Nanotubes
H. Yokoi, K. Uchida, and S. Takeyama
Aharonov-Bohm effect on the quantum states in singlewalled carbon nanotubes (SWNTs) is expected to cause
lifting of degeneracy in the energy bands of an electron in

Fig. 1. Magnetic field expansion of absorption spectra of the stretchaligned SWNTs film in the Voigt configuration with magnetic fields
and light polarization parallel to the SWNTs alignment. The symbols M
and S are corresponding to metallic SWNTs and semiconducting
SWNTs. The chiralities are also shown for the semiconducting
SWNTs. Arrows are the guide to the eye indicating field-induced splitting.

36

ISSP Activity Report 2004

Fig. 2. Comparison of magnetoabsorption spectra of the stretch-aligned
SWNTs film between the configurations B parallel and B perpendicular
to the alignment of SWNTs at 120 T together with a spectrum at zero
field.

SWNTs (Ajiki-Ando splitting)[1]. Recently, absorption andphotoluminescence in micelle-suspended SWNTs were
measured at magnetic fields to 45 T, and the splitting in thefirst band gaps of semiconducting SWNTs was found to bealmost in line with the Ajiki-Ando splitting.[2] However, thesplitting was not resolved for the second band gaps because
their spectral peak widths are broad, compared to the splitting amount. In addition, magneto-optical effect under magnetic fields applied perpendicularly to the SWNT axis was
not examined sufficiently because SWNTs were suspended
in water in their experiments. Both experimental proofs are
essential in order to make the assignment to the AharonovBohm effect conclusive. Especially, the former phenomenon
is important in the viewpoint that level crossing between thefirst subband and the second is predicted to occur at higher
magnetic fields.
We have conducted absorption measurements in stretchaligned SWNTs films[3] at magnetic fields to 120 T. Wellresolved spectral peaks associated with the second gaps ofthe semiconducting (6, 5) SWNT and a metallic SWNT,
assigned to (7, 7) tentatively, were observed to broaden
when the magnetic field was applied parallel to the SWNTs(Fig. 1). No significant modification of the peaks was recognized when the field was applied perpendicularly to the
SWNTs (Fig. 2), which supports the consideration that thepeak broadening is due to the Aharonov-Bohm effect. The
amount of the peak splitting for the semiconducting andmetallic SWNTs was estimated at 0.09 and 0.06 eV, respectively, which agrees semi-quantitatively with the Ajiki-Andosplitting, 0.099 and 0.052 eV, respectively. As excitonic
effect is not incorporated in their theory, more quantitative
review will be required for the precise study of the
Aharonov-Bohm phase in SWNTs. In metallic SWNTs,
magnetic field driven metal-semiconductor transition is
expected due to the Aharonov-Bohm effect. Our observationof splitting in the first gap in a metallic SWNT would show
an affirmative possibility of experimental observation of thetransition.

References[1] H. Ajiki and T. Ando, J. Phys. Soc. Jpn. 62, 1255 (1993).
[2] S. Zaric et al. Science 304, 1129 (2004).
[3] Y. Kim et al. Appl. Phys. Lett. 86, 073103 (2005).
Authors
H. Yokoia, N. Kurodaa, Y. Kimb, N. Minamib, S. Kazaouib, K. Uchida,
and S. Takeyamaa Dept. of Mechanical Eng. and Materials Sci., Kumamoto Univ.
b Nanotechnology Research Institute, AIST

Vortices in Superfluid 3He Induced by
Rotation in Parallel Plate Geometry
with 12.5µm Spacing
S. Ishikawa, T. Takagi, T. Mizusaki, and M. Kubota
The Vortex is well known phenomena in nature, forexample, tornado and typhoon on the Earth’s surface.
Vortices in quantum fluids, superfluid 3He and 4He have,
however, an interesting feature that circulation of velocity
around a core is quantized, with a minimum circulation
quantum number possible. When we rotate a bucket filledwith water, we observe a single vortex with continuously
changing strength. It is quite different when we have a superfluid in the bucket. The number of vortices changes according to the rotational speed because each vortex is quantized.
Superfluid vortices form cluster or lattice and rotate with thecontainer.
Superfluid 3He has many degrees of internal freedom andalso has many types of vortices depending on experimental
conditions due to its anisotropic gap structure in the A phase.
We put superfluid 3He A-phase in parallel plate geometry to
study what type of vortex appears by rotation. Stacking parallel plates with holes make many thin disc-shaped spaces
with 12.5µm thickness, where superfluid 3He is put in.
Spacing of 12.5µm is much longer than the coherence lengthof the superfluid 3He but is comparable to a healing length
on the texture of the order parameter. There are two candidates for vortices in A-phase in such a parallel plate geometry. One is called “phase vortex” and the other is “half quantum vortex”, which are quite different from vortices in bulk
superfluid 3He. Both vortices have been expected to exist in
the confined geometry. Our detection method is continuous
wave (cw) nuclear magnetic resonance (NMR).
We observed one absorption signal of NMR with negative frequency shift at rest and a satellite signal near theLarmor frequency under rotation (Fig. 1). In Fig. 2, the intensity of satellite signal is plotted as a function of rotational

Fig. 2. Increase of the intensity of the spin wave signal vs. rotation speed.

speed Ω [rad/s]. As increasing Ω from zero, satellite signal
appeared above a threshold value ΩFr and had maximum
value at Ωc. Further increase of Ω made satellite signal
decrease gradually up to our maximum speed Ωmax.
Appearance of satellite at ΩFr is attributed to textural transition of order parameter, so called Fréedericksz transition, by
the rotation induced counter flow. Our theoretical calculationof texture in parallel plate space under counter flow gives a
result that satellite frequency is in agreement with spinwave resonance frequency that is a collectively excited spin
motion in a deformed dipole interaction potential byFréedericksz transition. It should be noted that so far there
have been no vortex detected for Ω less than Ωc. Vortices areformed above Ωc. We can understand the existence ofvortices in parallel plate space by considering reduction ofsatellite signal intensity. Since vortices form a cluster andgive superfluid velocity as a rigid body rotation inside thecluster, the counter flow disappears inside the cluster anddecreases outside of it. So these changes of counter flow byvortices give rise to a reduction of satellite signal.
So far the type of vortex in parallel plate is not yet clear.
We have not observed any other satellite signal that shows anevidence of soft core vortex as in bulk liquid. This indicatesthat vortex in parallel plate has singular structure in the vortex core as phase vortex or half quantum vortex is expected
to have.
Authors
M. Yamashitaa, K. Izumina, Y. Kataoka, O. Ishikawab, T. Takagic, Y.
Sasakia, T. Mizusakia,d, and M. Kubota
a Department of Physics, Graduate School of Science, Kyoto University
b Graduate School of Science, Osaka City Universityc Department of Applied Physics, Fukui University
d Research Center for Low Temperature and Materials Sciences, Kyoto
University

Pressure Study of Ca3Ru2O7
Y. Yoshida and Y. Uwatoko

Fig. 1. NMR spectrum at 0.81 Tc. Horizontal line is normalized by thefrequency shift of bulk A-phase. At 0.01 rad/s, there are the liquidsignal of negative shift and the solid signal near the Larmor frequency.
At 1.80 rad/s, a spin wave signal appeared near the Larmor frequency.

Ruddlesden-Popper (R-P) type ruthenates (Sr, Ca)n+1RunO3n+1
have attracted many researchers since the discovery of thespin-triplet superconductivity in Sr2RuO4 (n=1). Beside thesuperconductivity, these ruthenates show a wide variety ofmagnetic and transport properties. In some ruthenates, suchas Sr3Ru2O7 and Ca2RuO4, applying pressure causes drasticchanges to their magnetic ground states. Among these R-P
type ruthenates, we selected a double-layered Ca-based
ruthenate, Ca3Ru2O7, showing an anti-ferromagnetic (AF)ordering below 56 K and a first-order transition at 48 K. The
crystal structure has the orthorhombic symmetry with Bb21m

ISSP Activity Report 2004

37

In these metallic region, we have fitted ρ(T) below 10 K
to the formula, ρ(T) = ρ0 + ATα. The exponent of α increases
from 1.18 to 1.45 with increasing pressure, while the otherparameters decrease. This indicates that the metallic behaviorof Ca3Ru2O7 is approaching that of the Fermi liquid metals
with increasing pressure.
References[1] Y. Yoshida et al., Phys. Rev. B 69, 220411 (2004).
[2] E. Ohmichi et al., Phys. Rev. B 70, 104414 (2004).
Authors
Y. Yoshidaa, S. I. Ikedaa, N. Shirakawaa, M. Hedo, and Y. Uwatoko
a Nanoelectronics Research Institute, National Institute of Advanced
Industrial and Technology (AIST)

Fig. 1. Temperature dependences of electrical resistivity for the current
normal to conducting RuO2 plane under various pressures.

space group, accompanying both the rotation and tilting of
RuO6 octahedra. The transport property of Ca3Ru2O7 ishighly anisotropic, and shows a quasi-two-dimensional metalin the ground state.[1] A structural change is accompanied by
the first-order transition, where a jump of lattice constant
was observed. [2]
In order to investigate the transport and the magnetic
properties of Ca3Ru2O7 under pressure, we have measured
the temperature dependence of the electrical resistivity underhigh pressure. Applied pressures were up to 10 GPa by using
a Cubic anvil apparatus.
Figure 1 shows temperature dependences of the electricalresistivity for the current along c-axis, i.e. normal toconducting RuO2 plane under various pressures. Both first-orderand AF transitions decrease steeply with increasing pressureand vanish around 3GPa. Small peaks around 10 K emerge
in the intermediate pressure range. These peaks are almostpressure independent, and do not relate to the transitions at
low pressures. The transport property finally changes frominsulating to metallic behavior above 8GPa, indicating
increase of electron transfer between RuO2 planes. These
results are summarized in a phase diagram, as shown in Fig.
2. The magnetic state in the intermediate region is still
unclear so that we need to measure magnetic properties
under this pressure range.

Fig. 2. Phase diagram of Ca3Ru2O7

38

ISSP Activity Report 2004

Discovery of Pressure-Induced
Superconductivity in CeNiGe3
M. Nakashima and Y. Uwatoko
High-pressure is useful method to control the magnetic
interaction and hybridization between the f electrons andconduction electrons. The crossover from the magneticallyordered state to the non-magnetic state under pressure,crossing the quantum critical point, is currently the mostinteresting issue in cerium compounds. Around the criticalpressure, a heavy fermion state or non-Fermi liquid behavior
appears at low temperatures. Moreover, superconductivity
appears around the critical pressure in some compounds. We
have continued in studying the effect of pressure on thecerium and uranium compounds. Among them, we report
CeNiGe3 antiferromagnetic Kondo compounds with theorthorhombic structure[1]. To apply high pressures, we used
three method, the indenter cell up to 4 GPa, the cubic anvil
cell up to 8GPa and diamond anvil cell up to 10 GPa.
Polycrystal sample of CeNGe3 was prepared by arc-melting
and annealing.

Fig. 1. Logarithmic scale of temperature dependence of the electricalresistivity under pressures in CeNiGe3, which was obtained by using
the cubic anvil cell.

References[1] P. Salamakha et al., J. Alloy. Compd. 236, 206 (1996).
[2] W. Assumus et al., Phys. Rev. Lett. 52, 469 (1984).
[3] S. Araki et al., J. Phys. Soc. Jpn. 68, 3334 (1999).
[4] M. Nakashima et al., J. Phys.: Condens. Matter. 16, L255 (2004).
Authors
M. Nakashimaa, K. Tabatab, A. Thamizhavela, T. C Kobayashic,
M. Hedo, Y. Uwatoko, K. Shimizub, R. Settaia, and Y. Onukia
a Graduate School of Science, Osaka University
b Research Center for Materials Science at Extreme Conditions, Osaka
Universityc Department of Physics, Faculty of Science, Okayama University,

Pressure Effect on Competition between
Charge Density Wave andSuperconductivity in ZrTe3:
Appearance of Pressure-Induced
Reentrant Superconductivity
K. Yamaya and Y. Uwatoko

Fig. 2. Pressure dependence of TN and Tsc (a), Tρmax (b), A(c) and ρ0 (d)values in CeNiGe3. The data shown by triangles, circles and squares
were obtained by the indenter, cubic and diamond anvil cells, respectively. Inset is the temperature dependence of resistivity at 6.5 GPa.

Figure 1 shows the logarithmic scale of temperaturedependence of the electrical resistivity at pressures up to 8.0
GPa in the temperature range of 2 to 300 K, which was
obtained by using the cubic anvil cell. The resistivity data at
different pressures are arbitrarily shifted downwards for
simplicity. The electrical resistivity at ambient pressure has abroad hump around 100 K (=Tρmax1) and also a broad peakaround 8 K (=Tρmax2), and decreases steeply below 5.5 K(=TN). These are characteristic features in the cerium Kondo
compound with antiferromagnetic ordering. The two characteristic features at Tρmax1 and Tρmax2 are found to merge at
5 GPa into a single resistivity peak at Tρmax = 50K. This single resistivity peak at 5 GPa shifts to higher temperatureswith further increasing pressure: Tρmax = 153 K at 8.0 GPa.
The antiferromagnetic ordering most likely disappears at 5.5
GPa (=Pc), as shown in Fig. 2(a). The overall temperaturedependence of the electrical resistivity around 5-6 GPa arevery similar to that in the heavy fermion superconductor
CeCu2Si2[2]. At 8.0 GPa, that is typically similar to thatobserved in a valence fluctuating compound such as CeNi,
where the 4f electron is itinerant[3].
〜We plot the A and ρ values in the Fermi liquid relation ofρ = ρ0 + AT 2 in Fig.2 (c) and (d). The A and ρ0 -values havemaximums around Pc . The A value at 5 GPa, 10.5µΩcm isthe same as that in CeCu2Si2 with an extremely large γ-valueof 1.1 J/K2mol[2]. The heavy fermion state is thus formed
around Pc = 5.5 GPa. In order to look for possible superconductivity around Pc, we measured the low-temperature resistivity by using the diamond anvil cell. Finally, superconductivity is observed in a wide pressure region from 4 to 10
GPa, as shown in inset of Fig. 2. The upper critical field
Hc2(0) at 6.5 GPa is roughly estimated as 2.0 T[4]. Further
studies of superconductivity are now in progress.

The application of hydrostatic pressure on the lowdimensional conductors generally increases three-dimensionality, leading to depression of the charge density waves(CDW) formation and enhancement of the superconductivity
by the restoration of the density of states at the Fermi level.
However, unusual pressure dependences of the CDW
transition temperature TCDW and the superconducting
transition temperature TC have observed in ZrTe3 which isone of transition-metal trichalcogenides MX3 that is wellknown as linear chain compounds, at least up to 1.1 GPa. [1]
The CDW formation is enhanced by pressure and the TCDW
reaches ~105 K at 1.1 GPa, while the superconductivity issuppressed and the TC goes down to 1.2 K at 0.5 GPa. A
greater pressure is expected to raise the three-dimensionality
in ZrTe3. Therefore, it would be very interesting to investigate the pressure dependences of TCDW and TC at highpressure. We investigated the pressure dependences of TCDW
and TC over a wide pressure range up to 11 GPa using a
cubic anvil pressure-cell to discuss a possible existence ofcompetition between the superconductivity and the CDW
formation. [2]Fig. 1 shows the pressure dependence of TCDW and TC
obtained for three samples, together with those for samples
measured earlier in the low pressure. As pressure increases,
TCDW initially increases, then starts to decrease at ~2 GPa

Fig. 1. Pressure dependence of TCDW (closed symbols) and TC (opensymbols) plotted on a logarithmic scale for three samples of ZrTe3.
Previous results are also shown at pressure below 1.1 GPa.[1]ISSP Activity Report 2004

39

and abruptly disappears to below 2.5 K between 5.0 and
5.5 GPa. Thus, CDW of ZrTe3 is sensitive to application of
external pressure. On the other hand, TC decreases withincreasing pressure and falls below 1.2 K at ~0.5 GPa. No
sign of superconducting transition is observed above 2.5 K in
the pressure range of 1.1 - 5 GPa, but the superconducting
transition emerges beginning at ~5 GPa. TC increases steeply
with increasing pressure up to 11 GPa. In contrast to
the abruptly disappearance of TCDW, the temperaturedependence of resistance in the metallic state varies systematically for pressure from 2 to 11 GPa and any anomalouschange is not observed around 5 GPa, showing that theabruptly disappearance of TCDW near 5 GPa is not due to a
structure phase change. Thus, we conclude that superconductivity observed above 5 GPa is induced by a change in the
Fermi surface (FS) under pressure. This is the first observation of pressure-induced reentrant superconductivity. TC in
the pressure range of 0.5 - 5 GPa is shown by extrapolationfrom the pressure range of P < 0.5 GPa and P > 5 GPa. The
minimum TC was estimated to be around 2 GPa, where isjust a pressure corresponding to the peak of TCDW. Such aremarkable pressure dependent competition between TCDW
and TC has not been reported for other systems of lowdimensional conductors.
Analyzing the size of the resistance anomaly due to the
CDW formation, it was found that the intricate competition
between CDW and superconductivity is explained by thechange in the reduced area of the FS due to CDW formation.
A notable feature of the FS of ZrTe3 is the differing dimensionality of quasi-1D, dual quasi-1D+3D and 3D. [3,4] The
quasi-1D FS sheets have Te 5px character, while the 3D FS
has dominant Zr 4d character. The 1D sheets are responsible
for CDW formation, while the dual quasi-1D+3D characteris responsible for superconductivity. [3,4] Therefore, thecompetition between CDW and superconductivity shows thestrong hybridization of Te 5px and Zr 4d bands. The detailproperties of pressure-induced reentrant superconductivity
will be published elsewhere. [5]References[1] K. Igarashi, S. Yasuzuka, K. Inagaki, S. Tanda, Y. Okajima,
M. Hedo, Y. Uwatoko, and K. Yamaya, J. de Phys. IV 12, 97 (2002).
[2] R. Yomo, K. Yamaya, M. Abliz, M. Hedo, and Y. Uwatoko, Phys.
Rev. B 71, 132508 (2005).
[3] K. Stowe and F.R. Wagner, J. Solid State Chem. 138, 160 (1998);
C. Felaer, E.W. Frinckh, H. Kleine, F. Rocker, and W. Tremel,
J. Matter. Chem. 1, 1787 (1998).
[4] T.Yokoya, T. Kiss, A. Chainani, S. Shin, and K. Yamaya, Phys.
Rev. B71, 140504 (2005).
[5] M. Abliz, M. Hedo, Y. Uwatoko, R. Yomo, and K. Yamaya, Phys.
Rev. Lett. (in preparation).
Authors
R. Yomoa, K. Yamayaa, M. Alibe, N. Hedo, and Y. Uwatoko
a Dept. of Appl. Phys., Hokkaido University.

Observation of Two-Photon
Above-Threshold Ionization of Rare
Gases by XUV Harmonic Photons
S. Watanabe and T. Nakajima
In order to measure attosecond pulses in the extreme
ultraviolet (XUV), the observation of single-color two-photon above threshold ionization (ATI) is an important
cornerstone toward the "full and direct" characterization ofultrashort pulses in the XUV~soft X-ray range. This is40

ISSP Activity Report 2004

Fig. 1. Photoelectron spectra of two-photon ATI in Ar (a), Xe (b), andHe (c).

because (1) for XUV photons even a single-photon absorption will bring atoms above ionization threshold and hence
ATI is necessarily involved for any nonlinear processes, and(2) the accuracy of autocorrelation-based pulse measurement
has no fundamental limitation in terms of the measurable
pulse width. In the shorter wavelength (XUV~soft X-ray),however, we should keep in mind that bright light sources
are not easily obtained and the corresponding dipole
moments are much smaller than those in the visible~IR
range, since large transition energy usually means small
overlap of wavefunctions. About the theoretical aspects forthe description of two-photon ATI, we are not aware of any
calculations which resolve fine structure of the ionic core.
In this study, we report the first experimental observationof single-color two-photon ATI in Ar, Xe, and He in the
XUV range at 25 eV photon energy, and compare with ourtheoretical results. Since the single-color two-photon ATI
signal by XUV photons is very weak, a special detection
technique is needed. This was realized by the use of theenergy-resolved electron counting system at a low repetition
rate of 40-100 Hz together with strong 25 eV radiation
generated by the 5th harmonic of our KrF/Ti:Sapphire hybrid
laser system.
The photon energy of 25 eV is already above thefirst ionization thresholds of all rare gases. Note that thetwo-photon absorption of 25 eV photons bring Ar and Xe
atoms above the double ionization thresholds. Thus two-photon double ionization as well as two-photon ATI can takeplace for Ar and Xe. However, the two-photon double
ionization cross section is typically about one order ofmagnitude smaller than that for the two-photon ATI crosssection. Besides, the photoelectron spectrum for the twophoton double ionization appears as a background, showing
no peak structure. Therefore, it is a natural choice, in particular as a first attempt in the XUV range, to try to observe
two-photon ATI. The peaks due to two-photon ATI should

be located at 34.24 eV and 34.06 eV in Ar, 37.87 eV and
36.56 eV in Xe, 25.41 eV in He, respectively.
Figure 1(a) shows the two-photon ATI spectrum of Ar.
The two peaks separated by 0.18 eV were resolved. Next
the two-photon ATI spectrum of Xe is shown in Fig. 1(b).
In Fig. 1(b), only a single peak corresponding to the coreof p5[2P3/2] was observed. The background noise may
have covered the two-photon ATI signal for the p5[2P1/2]
core. Finally the two-photon ATI spectrum of He is shown
Fig. 1(c).
References[1] N. Miyamoto, M. Kamei, D. Yoshitomi, T. Kanai, T. Sekikawa,T. Nakajima, and S. Watanabe, Phys. Rev. Lett. 93, 083903 (2004).
[2] T. Nakajima and S. Watanabe, Phys. Rev A 70, 043412 (2004).
Authors
N. Miyamoto, M. Kamei, D. Yoshitomi, T. Kanai, T. Sekikawa,T. Nakajimaa, and S. Watanabea Institute of Advanced Energy, Kyoto University

Strain Distributions under the
SiO2/Si(001) Interface Revealed by thePhase-Sensitive X-ray Diffraction(PSXD) Technique
W. Yashiro and T. Takahashi
Strain near an interface affects its electronic structure, but
a full understanding of such strains is still lacking even in
the case of SiO2/Si, which has been applied to electronic
devices since 1960s. We have developed a new technique,the phase-sensitive X-ray diffraction (PSXD) technique,which is a powerful way to characterize strain fields near
crystal surfaces. By using this technique we have revealed
that there is a small strain field extending over mesoscopicrange depth (up to several hundred of nm) under the SiO2/Si
interface and having a static fluctuation in the lateral direction [1]. This technique can also be applied to investigate

Fig. 2. A schematic view of the distribution of strain fields under the
SiO2/Si interfaces in the cases of Kr/O2 plasma oxidation and thermaloxidation at 900℃, which was revealed by using the PSXD technique.
It was shown that the distribution of strain field under the Kr/O2 plasmaoxide layer a few nanometer thick was different from that under thethermal oxide layer very near to the interface. Here ∆D(z) is the total
displacement atomic planes under the SiO2/Si interface and z is thedepth, the origin of which is defined at the interface.

distribution of strain field under the interface.
The PSXD technique is an application of a phenomenon,
modulation of the intensity of the crystal-truncation-rod(CTR) scattering under an excitation of a Bragg reflection[1-3], which is an interaction between a two-dimensionallydiffracted wave (CTR scattering) and a three-dimensionallydiffracted (Bragg reflection) wave. It was shown that themodulation profile can be characterized by two parameters:
the phase shift, which represents the dip or peak positionof the modulation profile, and the visibility. The phase shift
can be simply interpreted into the sum of displacements ofatomic planes under the interface, which is due to the strain
field extending over mesoscopic-range depth, while thevisibility gives information on static fluctuation of the total
displacement in the lateral direction.
Figure 1 shows an illustration of strain field under a
SiO2/Si interface which was revealed by the PSXD technique[1]. The experimentally obtained phase shift was interpreted
into a total displacement of -0.16 Å under the interface
projected onto the direction perpendicular to the 004 plane.
On the other hand the experimentally obtained visibility
indicated that the total displacement has a static fluctuationof at least ! 0.13 Å in the direction parallel to the interface.
Another example of the result of the PSXD technique isshown in Fig. 2, where the distributions of strain fields under
the SiO2/Si interfaces are illustrated in the cases of Kr/O2
plasma oxidation and thermal oxidation at 900℃. Thesefeatures revealed by the PSXD technique are expected
to provide a new window to understand the oxidation
mechanism of Si surface.
References[1] W. Yashiro, K. Sumitani, T. Takahashi, Y. Yoda, and K. Miki,
Surf. Sci. 550, 93 (2004).
[2] T. Takahashi and S. Nakatani, Surf. Sci. 326, 347 (1995).
[3] W. Yashiro, K. Sumitani, Y. Yoda, and T. Takahashi, Jpn. J. Appl.
Phys. 42, 6658 (2003), and references therein.

Fig. 1. An illustration of the strain field in a Si(001) wafer on which athermal oxide layer was formed. The open circles represent the sites
of atoms or unit cells in bulk crystal, and the solid circles represent
the position of them in the strained layer near the interface. The
arrangement of the experiment was set to be particularly sensitive tostrain fields distributing mesoscopic-range depth. The phase shift ofmodulation profile can be simply interpreted into the sum of displacements of atomic planes under the interface projected onto the direction
perpendicular to the 004 plane. Our experimental results showed that
there is a total displacement of -0.16 Å in the direction perpendicular tothe crystal surface. On the other hand the experimentally obtained
visibility indicates that the total displacement has static fluctuation in
the direction parallel to the interface. The visibility was interpreted intoa static fluctuation of at least ! 0.13 Å in the lateral direction.

Authors
W. Yashiroa, K. Sumitani, Y. Yodac, K. Mikia,b, K. Takahashid,
T. Hattorid, and T. Takahashia Nanomaterials Laboratory (NML), National Research Institute forMaterials Science (NIMS)b Graduate School of Pure and Applied Sciences, University of Tsukuba
c Japan Synchrotoron Radiation Research Institute (JASRI)d Department of Electrical and Electronic Engineering, Faculty ofEngineering, Musashi Institute of Technology

ISSP Activity Report 2004

41

New Type of Universality on N'eel
Temperatures of Quasi-LowDimensional Antiferromagnets
C. Yasuda, S. Todo, and H. Takayama
While the genuinely two-dimensional (2D) and onedimensional (1D) antiferromagnetic Heisenberg (AFH)models cannot display long-range order except at zerotemperature, weak inter-layer or inter-chain couplings, J',
which always exist in real materials, lead to a phasetransition at a finite N'eel temperature TN. So far, theJ'-dependence of TN was calculated by exactly treating
effects of the strong interaction J in the 2D or 1D system, but
by using mean-field-type approximations for effects of J'.
The results are widely utilized for analyses of experimental
measurements for quasi-low-dimensional (QLD) antiferromagnets, e.g., the quasi-2D (Q2D) high-Tc superconductor
La2CuO4, the quasi-1D (Q1D) antiferromagnet Sr2CuO3, andso on.
Recently we have performed large-scale Monte Carlo(MC) simulations on anisotropic cubic lattices as a subject of
the joint-use of the ISSP supercomputer system. Besides
useful and quantitatively more accurate formulae for TN,
we obtained a new type of universal behavior of TN
for the QLD AFH models.[1] Our numerical work showsthat a renormalized coordination number defined by
ζ(J') /1/J'χs(TN) becomes constant ζ(J') . ζd = kdzd notdepending on J' for J' < J'c - 0.1J as shown in Fig. 1. Here,χs(T) is the staggered susceptibility of the 2D or 1D model attemperature T and zd is the coordination number, z2 (1) = 2 (4)for the Q2D (Q1D) system. When kd = 1, this relation reduces
to the well-known RPA result: zdJ'χs(TN) = 1. Interestingly,
the values of kd are found to be common within our numerical accuracy for S=1/2, 1, 3/2 and 3.
For the Q2D systems, TN(J') "- 1 / ln(J'/J) is expected
at small J'/J for both quantum and classical systems fromtheir common exponential forms of χs at T " 0. Figure 1 (a)shows that the values of ζ(J') and so k2 = 0.65 are universal,
or independent of the spin size S. Using the analytical formof χs obtained in the renormalized classical regime of the
non-linear σ model (NLσ M), our universal relation is compatible with the one derived analytically for the S= 1/2 Q2D
AFH model in the limit J'/J " 0.[2] For the Q1D systems,
due to the different forms of χs, we observe that
TN(J') " J’ J at small J'/J for S = 3, while TN(J') " J'/J
with logarithmic corrections for S=1/2. In spite of this difference, as shown in Fig. 1 (b), the values of ζ(J') are universal
with k1= 0.695 again for J'/J h0.1. Moreover, the value of k1
is quantitatively consistent with the result k1 - 0.70 of themodified RPA theory, in which the 1/z1 corrections to theinter-chain mean-field theory have been obtained by meansof the bosonized Hamiltonian of the S=1/2 Q1D AFH
model.[3]The independence of ζd on the spin size S for the QLD
systems suggests a universality of corrections to RPA for
J' %J. Since in this temperature regime the physics of allthese models should be well described by an anisotropic
NLσ M in the renormalized classical regime, we conjecture
universal corrections to RPA also for the NLσ M.
References[1] C. Yasuda et al., to be published in Phys. Rev. Lett. (condmat/0312392).
[2] V. Yu. Irkhin and A. A. Katanin, Phys. Rev. B 55, 12318 (1997).
[3] V. Yu. Irkhin and A. A. Katanin, Phys. Rev. B 61, 6757 (2000).
Authors
C. Yasudaa, S. Todob, K. Hukushimac, F. Aletd, M. Kellere,
M. Troyere,f, and H. Takayama
a Department of Physics and Mathematics, Aoyama Gakuin University
b Department of Applied Physics, University of Tokyoc Department of Basic Science, University of Tokyod Servie de Physique Th eorique,'
CEA Saclay
e Theoretische Physik, ETH Z up richf Computational Laboratory, ETH Z up richSuperconductivity inWater-Intercalated Tantalum Sulfides
M. Nohara and F. Sakai

Fig. 1. Values of ζ(J')/zd of the Q2D (a) and Q1D (b) AFH models.
They are evaluated from TN which are obtained from the finite-size
scaling analysis on our numerical data for the QLD system and χs(TN)which are obtained also from MC simulations interpolated near T = TN.
An exception here is χs of the classical 1D model, for which its known
exact solution is used. Another comment is on the S=1 Q1D system,that simulations at lower temperature than the Haldane gap of the isolated chain are hardly carried out and so our analysis is limited in therange of J'/J $ 0.05. The error bar of each point is smaller than thesymbol size unless given explicitly.

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ISSP Activity Report 2004

Water, one of the most common molecule around human
life, has not been recognized its major role in solid statephysics until the discovery of watery superconductivity inthe layered cobalt oxide NaxCoO2 [1]. The superconductivity
at about 5 K emerges when the water molecules are intercalated between the CoO2 and Na layers, namely, the CoO2
layers are separated by a "bilayer" of water molecules.
Remarkably, the superconductivity disappears when the
CoO2 layers are separated by a "monolayer" of water molecules, or the water molecules are absent between the layers.
In this joint research, we have discovered another familyNax(SbS)1+δ(TaS2)2, this indicate that the water molecules
are favorable to superconductivity in the sulfides as wellas in the Co oxide. We naively expect that the Tc is reducedby random Coulomb potential created by Na ions on the
conducting TaS2 layers for the anhydrate, and the potential iseffectively shielded by the water molecule indebted to its
large polarization. The detail has been published in Ref. 2.
References[1] K. Takada et. al., Nature 422, 53 (2003).
[2] N. Katayama, M. Nohara, F. Sakai, and H. Takagi, J. Phys. Soc.
Jpn. 74, 851 (2005).
Authors
N. Katayamaa, M. Noharaa, H. Takagia, and F. Sakaia Department of Advanced Materials Science, University of Tokyo

X-ray Study at Low Temperature andUnder Pressure in (TMTSF)2FSO3
J. Yamaura and W. Kang
Fig. 1. Schematic view of the crystal structure of "parent" compound(MS)1+δ(TaS2)2 and "bilayer" hydrate Nax(H2O)y(MS)1+δ(TaS2)2. The
water molecules are intercalated between the TaS2 and Na layers.

of water-intercalated superconductors in novel hydrate sulfides Nax(H2O)y(MS)1+δ(TaS2)2 with M = Sn, Pb, Sb, and Bi.
The parent compound (MS)1+δ(TaS2)2 consists of a pair of(TaS2)2 layers and a rock-salt layers of MS, as shown in Fig.
1. Na ions and water molecules are intercalated between theadjacent TaS2 layers and anhydrate Nax(MS)1+δ(TaS2)2 and"bilayer" hydrate Nax(H2O)y(MS)1+δ(TaS2)2 are obtained. The
chemical composition of these materials was successfully
determined at Materials Design and Characterization
Laboratory, ISSP, by using various facilities including anelectron-probe microanalyser (EPMA). Figure 2 shows
superconducting transition observed for the M = Sb series.
The transition temperature Tc increases as the Na ions andwater molecules are intercalated. Remarkably, the hydrate
exhibits the highest Tc. Since the Na content is the same forboth the hydrate Nax(H2O)y(SbS)1+δ(TaS2)2 and anhydrate

Fig. 2. Temperature dependence of magnetic susceptibility forparent (SbS)1+δ(TaS2)2, anhydrate Nax(SbS)1+δ(TaS2)2, and hydrateNax(H2O)y(MS)1+δ(TaS2)2. Superconducting transition temperatureis enhanced by water molecules.

Bechgaard salt (TMTSF)2FSO3 is an interesting molecular conductor, indicating the complex pressure-temperaturephase diagram as shown in Fig. 1 [1]. The symbols aredefined as the phase boundary: metal-insulator (I), anomaly
in resistivity (II, III, VI), metal-superconductor (IV), andmetal-metal (V). The FSO3- anion having a finite electric
dipole moment is presumably related to an additional degreeof freedom. Here, we investigated the origin of the transitions by X-ray diffraction measurements at low temperatureand under pressure.
A single-crystal superstructure analysis including the(1/2,1/2,1/2) reflections were performed below themetal-insulator transition (89K) at ambient pressure. The
orientational ordering of the anions, the tetramerization andthe charge disproportionation of TMTSF molecules witha symmetry breaking were determined. The net momentof the electric dipoles of anions is directed to the TMTSF
column (a-axis), which suggests the existence of ferroelec-

Fig. 1. Pressure-temperature phase diagram of (TMTSF)2FSO3. The
symbols are defined as the phase boundary: metal-insulator (I),
anomaly in resistivity (II, III, VI), metal-superconductor (IV), andmetal-metal (V).

ISSP Activity Report 200443

tricity. From the oscillation photograph using an imaging
plate and a diamond anvil cell, we observed various
types of satellite reflections: q1=(1/2,1/2,1/2), q2=(0,0,1/2),
q3=(0, .0,0.17 !0.02) and q4=(0,1/2,0), as shown in Fig. 1.
These are thought to originate from the orientational orderingof anions. In addition, a symmetry change from the triclinic
P-1 to the monoclinic Pm was observed accompanied with
the q4-superlattice through the transition V.
Reference[1] Y. J. Jo, E. S. Choi, Haeyong Kang, W. Kang, I. S. Seo, andO. H. Chung, Phys. Rev. B 67, 014516 (2003).
Authors
J. Yamaura, Y. J. Joa, Haeyong Kanga, O. H. Chungb, and W. Kangaa Dept. of Physics, Ewha Womans University,b Dept. of Physics, Sunchon University

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ISSP Activity Report 2004

ISSP Workshop

1. Recent progress and new frontiers of surface science using LEEM (low energy
electron microscope) and PEEM (photoemission electron microscope) April 26-27, 2004
T. Kinoshita and T. Koshikawa
LEEM and PEEM are relatively new microscopic
methods and attracted much attention because these give
us a variety of experimental possibilities such as imaging,diffraction, micro-spectroscopy, dynamical observation andso on. The studies in this field become very active recently
in Japan. This workshop was organized for the discussion
and communication between the scientists who are using
LEEM and/or PEEM. For such kind of microscopy
techniques, the high brilliant light source in VUV andsoft-X-ray regions is necessary, namely Super-SOR. The
user's communities of the Super-SOR co-organized theworkshop.
This workshop was a first full-scale meeting for
LEEM/PEEM in Japan. Therefore some lectures concerning to LEEM and PEEM principles and recent activities
were organized together with the oral- and the poster-sessions. It was confirmed that the LEEM/PEEM are very useful for thestudies of the dynamical observation of thin-films and nanostructure growth, catalysis reaction, element-specific magnetic
domain observation, and characterization of devices/ recording media etc. Further, some PEEM apparatus have been installedin the synchrotron radiation facilities, PF, HiSOR, and Spring-8. Some of them have been opened to the outside-users. The
demands from users and information concerning to the apparatus were discussed.
At the end of the workshop, the present status of the Super-SOR project was introduced. The requests from the users to thebeamlines were also discussed, for example, resolution, beam-size, polarization switching etc. Especially in the field of
LEEM/PEEM, high-brilliance light source is most important facilities. Frontiers of the surface science will be surely developedby the combination of Super-SOR and high-performance LEEM/PEEM.
http://www.issp.u-tokyo.ac.jp/contents/seminar/short/tanki20040426.html
http://www.issp.u-tokyo.ac.jp/labs/sor/button/leempeem-all.pdf

2. Peculiar magnetic properties in itinerant-electron systems and their application
to magnetic material
May 13-15, 2004
H. Yamada
Theoretical and experimental studies on itinerant-electron magnetism were carried out in 1970' and 1980' intensively. Thosebasic studies have made a strong contribution to the recent progress in magnetism for various kinds of intermetallic compounds. These developments in this field are also much indebted to a rapid improvement of experimental techniques undermultiple extreme conditions of high magnetic field and high pressure, and to the improvement of sample preparation.
Furthermore, it became possible to discuss theoretically the peculiar magnetic properties observed in 3d transition-metal compounds, by using calculated band-structures of electrons and by taking into account the effect of spin fluctuations. Under strong
collaborations between theory and experiment, the basic study on magnetism in the itinerant-electron system has been developed intensively in Japan. On the other hand, it is not too much to say that the recent progress in the studies on applied science,
not only of giant magnetostrictive, giant magnetocaloric materials but also of ferromagnetic shape memory, thermoelectric, andhalf-metal materials, is based on the basic researches of magnetism in the itinerant-electron system. In order to make a strong
collaboration between these basic and applied sciences further, the present meeting was held. Including two foreign researchers,
37 papers on current topics in basic and applied magnetism of the itinerant-electron system were presented. About 100 participants, including graduated students, have attended to this meeting and a lot of exciting discussions have been done.
http://www.issp.u-tokyo.ac.jp/contents/seminar/short/tanki20040513.html

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45

3. Physical properties and energy landscapes of extremely non-equilibrium systems
August 9-10, 2004

O. Yamamuro, H. Takayama, and M. Shibayama
Recently, the non-equilibrium systems extremely apart from their equilibrium states attract attentions of many scientists.
Various amorphous materials, polymer and supramolecular systems, and biomaterials such as proteins are included in this category. Their potential energy and free energy surfaces in configurational space, so-called "energy landscape", have many basinscorresponding to their many metastable states. It is considered that the shape of the basins and the transformation among thebasins dominate physical properties, relaxation processes and functions of the systems. The present workshop consisted of 21
oral and 21 poster presentations for the experimental and theoretical studies on glass transitions, amorphous ices, spin glasses,
polymer crystallization, gels, proteins, etc. About 80 participants actively discussed the new theoretical approach for the landscape, the explanation of various physical properties using the landscape, and the future development for the landscape science.
http://yamamuro.issp.u-tokyo.ac.jp/workshop1.html

4. Frontier and new field of science opened by VUV/SX third generation
high-brilliance synchrotron radiation
December 9-11, 2004
H. Daimon, A. Kakizaki, J. Yoshinobu, and T. Kinoshita
The project for constructing a new third-generation synchrotron radiation facility dedicated to sciences in VUVand Soft X-ray (SX) region has been eagerly awaited bymany people for a long time. Although there is no thirdgeneration VUV/SX ring in Japan, many researchers are
conducting unique and cutting-edge science in this fieldusing second-generation rings or those in foreign countries.
One aim of this symposium is to survey frontier condensed-matter and nanosciences conducted by advanced
Japanese researchers. A lot of presentations and active discussions occurred throughout the three days. It was recognized that many fruitful advanced activities are being donein this field by young scientists and new fields will be created by the new third-generation synchrotron radiation
facility. There are many users who desire to use the ring.
Another aim of this symposium is to increase the number of users of the new third-generation synchrotron radiation facility. The Kashiwa campus, which is the most probable location of the ring, is close to other scientific and technologicalinstitutes, such as Tokatsu Techno Plaza, National Cancer Center, National Research Institute of Police Science, and Faculty of
Horticulture of Chiba University. Only a one-day trip would be required to use the facility for the people in Tokyo bay area,
where many potential users exist in industry of nano-analysis, nano-fabrication, and medical- or bio-science. We asked someresearchers and technical experts of these industries to present their request during the symposium. A ring which fulfills theserequirements is hoped for.
http://www.issp.u-tokyo.ac.jp/contents/seminar/short/tanki20041209.html

5. French-Japanese meeting on high magnetic field

December 6, 2004

S. Takeyama and M. Takigawa
Static high magnetic field provides valuable opportunities to discover novel phenomena in condensed matter science.
Quantum phase transitions induced by magnetic field in spin systems, organic conductors and semiconductors, and novel magneto optical effects are good examples. This workshop was organized to stimulate collaboration between Japanese scientists
interested in research using static high magnetic field and the Grenoble High Magnetic Field Laboratory (GHMFL), which provide excellent experimental environment at high field up to 33 tesla and at low temperature. In the first half of the meeting,
French participants including Dr. G. Martinez, the director of GHMFL, explained the operation of the facility, technical aspectsof magnet design, capabilities for various condensed matter experiments such as NMR, EPR, optical measurements and transport measurements. In the second half, the Japanese participants presented several experimental proposals as well as distinct
features of the high field facility in Tohoku University. We hope that fruitful collaboration will come out as a results of suchworkshop.
http://www.issp.u-tokyo.ac.jp/labs/extreme/himag-forum/page013.html

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ISSP Activity Report 2004

6. The structure of the Si(111)- 3 # 3 -Ag surface and its phase transition
December 14- 15, 2004

T. Takahashi
The structure of the Si(111)- 3 # 3 -Ag surface has been attracting interests over thirty years since the first observation of
the surface by low energy electron diffraction. After a long controversy the structure at room temperature was determined by
x-ray diffraction, but recent studies by first-principles calculations and STM at low temperature suggest that a slightly different
structure with a rotation is more stable at low temperatures. In this workshop the structure of the surface at both high and low
temperature phases as well as the phase transition is intensively discussed.
http://www.issp.u-tokyo.ac.jp/contents/seminar/short/tanki20041214.html

7. To new science with SANS, QENS, and NSE

January 26-27, 2005

M. Shibayama
The Neutron Science Laboratory, (NSL-ISSP) has upgraded three major instruments covering the fields of soft matterphysics, glasses, mixtures, and biological systems. The instruments were SANS-U (Small Angle Neutron Scattering
Instrument, University of Tokyo), iNSE (New iSSP Neutron Spin Echo Spectrometer), and AGNES (Angle Focusing Cold
Neutron Spectrometer). The purposes of the workshop were to demonstrate the performance of these instruments and to
discuss the recent topics in these fields. The workshop consisted of instrumentation and cross-disciplinary sections, namely,
introduction of the upgraded instruments, biology and high performance polymer, new aspects of soft matter physics, physics
of mixtures, and slow dynamics of glasses, etc. Active discussions with 65 participants related to 25 oral presentations and 23
posters were quite meaningful to predict the directions of new sciences. The presentation record of the workshop was issued as
an NSL News Letter 2005-1 in June, 2005.
http://shibayama.issp.u-tokyo.ac.jp/ISSPWS/ISSPWS0501.html)

8. Electronic transport in magnetic systems

February 14-15, 2005

Y. Iye, T. Ono, Y. Otani, T. Kato, and S. Katsumoto
Study of electronic transport in magnetic systems has a long history in magnetic materials such as transition and rare earth
metals and alloys. In recent years, the scope has been immensely widened by the advent of diluted magnetic semiconductors
and transition metal oxides. Research in this field is entering a new phase by the ability of fabricating artificial structures by thetechnical developments of thin film growth and microfabrication. On the theoretical side, there is growing interest in novel
quantum transport phenomena associated with geometrical phase. Recent topics include, electrons scattering at the domainboundary in ferromagnetic metals, control of domain wall motion by spin polarized current, observation of domain wall
dynamics, spin injection in magnetic and non-magnetic semiconductor hybrid structures, and spin Hall effect. In this workshop,
active researchers in this field presented their latest results and exchanged the ideas.
http://iye.issp.u-tokyo.ac.jp/Workshop/ISSP-workshop.htm

9. High pressure material seminar21:Frontier of Megabar Science

March 4, 2005

Y. Uwatoko
A high-pressure technology has contributed to advancements of researches in solid state physics. The number of thesubjects increases when a new high-pressure technology appeared, and a lot of new physical properties have been found. New
physical phenomenon and function seems to be still waiting to be discovered by us under the high pressure. This seminar was
programmed with 3 sessions of; technology for very high-pressure generation, search for new physical properties underpressure, high-pressure synthesis of new functional materials. Organizer proceeded to a discussion in above subjects in one
megabar (1 million atmospheric pressure) class pressure region.
http://www.issp.u-tokyo.ac.jp/contents/seminar/short/highpressure21-20050304.html

ISSP Activity Report 2004

47