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Yosuke Takasu, Yoshiro Takahashi
2009 Volume 78 Issue 1 Pages
012001
Published: January 15, 2009
Released on J-STAGE: December 28, 2011
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We describe in detail our recent experiments on quantum degenerate gases of ytterbium (Yb) atoms. Up to now Bose–Einstein condensates of
174Yb and
170Yb, and a Fermi degenerate gas of
173Yb have been realized by efficient evaporative cooling in a crossed far-off resonant trap. Our studies showed that the efficient escape from the trap and rapid thermalization are important for efficient evaporative cooling. We also describe some recent experiments using Yb Bose–Einstein condensates such as the achievement of a scalar atom laser, the observation of an optical coherent transient, and successful loading into an optical lattice. Finally, the future prospects using Yb quantum degenerate gases are discussed in detail.
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Fusae Kaneko, Kazutoshi Yagi-Watanabe, Masahito Tanaka, Kazumichi Naka ...
2009 Volume 78 Issue 1 Pages
013001
Published: January 15, 2009
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Natural circular dichroism (CD) of alanine (Ala) and valine (Val) films were measured in vacuum ultraviolet region using a polarizing undulator as a circularly polarized light source. Compared with absorption spectra, CD spectra showed clear differences between Ala and Val films. In order to explain these differences, a time-dependent density functional theory was applied to calculated CD spectra. The calculated CD spectra showed good agreement with the experimental CD spectra.
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Atsushi Fukumi, Itsuo Nakano, Hajime Nanjo, Noboru Sasao, Seiichi Sato ...
2009 Volume 78 Issue 1 Pages
013201
Published: January 15, 2009
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The best method of measuring CP violating effect in neutrino oscillation experiments is to construct and use a neutrino beam made of an ideal mixture of \\barν
e and ν
e of monochromatic lines. The conceptual design of such a beam is described, together with how to measure the CP-odd quantity. We propose to exploit an accelerated unstable hydrogen-like heavy ion in a storage ring, whose decay has both electron capture and bound beta decay with a comparable fraction.
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Masao Takamoto, Hidetoshi Katori
2009 Volume 78 Issue 1 Pages
013301
Published: January 15, 2009
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We investigated the coherence of spin-polarized
87Sr atoms trapped in a light-shift-free one-dimensional optical lattice during their interaction with a clock laser on the
1S0–
3P0 transition. Collapses and revivals appeared for more than 50 Rabi cycles, attributed to the thermal distribution of discrete vibrational states in the lattice potential. The population oscillation in the clock states lasted more than 1 s, demonstrating high immunity from decoherence. This long atomic coherence suggests the feasibility of Pauli blocking of collisions in optical clock excitation.
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Akio Sanpei, Kensuke Oki, Ryuya Ikezoe, Takumi Onchi, Ken-Ichi Murata, ...
2009 Volume 78 Issue 1 Pages
013501
Published: January 15, 2009
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A neoclassical equilibrium for low-aspect-ratio reversed field pinch (RFP) plasma is reconstructed from initial experimental results of the standard discharge in a low-aspect-ratio RFP device (RELAX). We estimate the magnitude of the bootstrap current, which is a self-induced plasma parallel current, from the reconstructed equilibrium, and illustrate how the bootstrap current depends on plasma parameters.
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Yuki Fuseya, Masao Ogata
2009 Volume 78 Issue 1 Pages
013601
Published: January 15, 2009
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We study the triangular
t–
J model with multiple spin exchange interactions using exact diagonalization of small clusters, as a model of monolayer liquid
3He. A phase where the energy spectrum suggest the behaviors of spin–charge separation is realized in the doped-Mott region due to the competition between ferromagnetic two-spin and antiferromagnetic four-spin exchange interactions. This behavior gives an interpretation of the double peaked heat capacity recently observed in monolayer liquid
3He adsorbed on a graphite.
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XiaoJun Liu, Yutaka Moritomo, Tomoyuki Matsuda, Hayato Kamioka, Hiroko ...
2009 Volume 78 Issue 1 Pages
013602
Published: January 15, 2009
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Hydrostatic pressure effect on Prussian blue type network in RbMn[Fe(CN)
6] has been investigated by high-pressure vibrational spectroscopy. Frequencies of the CN stretching modes increase as pressure increases:
dhω⁄
dP=6.4 cm
−1/GPa for
A1g mode and 4.3 cm
−1/GPa for
Eg mode. With further increase of pressure beyond ≈2 GPa, slope of the hω–
P curve becomes fairly gradual. We ascribed the behavior to the in-plane rotation of FeC
6/MnN
6 octahedra, since it compensates the pressure-induced contraction in volume.
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Kazumasa Hattori, Hirokazu Tsunetsugu
2009 Volume 78 Issue 1 Pages
013603
Published: January 15, 2009
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We investigate a lattice of interacting anharmonic oscillators by using a mean field theory and exact diagonalization. We construct an effective five-state hopping model with intersite repulsions as a model for β-pyrochlore AOs
2O
6 (A=K, Rb or Cs). We find the line of the first order phase transition from large to small oscillation amplitude phases as temperature decreases. Our theory can explain the origin of the mysterious first order transition in KOs
2O
6. We also discuss the possibility of a phase with local electric polarizations.
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Tetsuji Okuda, Taizo Kishimoto, Kazuma Uto, Takahisa Hokazono, Yoshino ...
2009 Volume 78 Issue 1 Pages
013604
Published: January 15, 2009
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Dimensional crossover from anisotropic-three-dimensional (3D) to 2D low-energy magnetic excitations was found in delafossite oxide Cu
1−xAg
xCrO
2 having a spin-3/2 antiferromagnetic (AF) triangular lattice. The crossover is evidenced by a decrease in AF transition temperature (
TN), distinct 2D magnetic excitations above
TN for Cu
0.85Ag
0.15CrO
2, a disappearance of a peak of magnetic specific heat (
Cmag) around
TN, and a successive change from
T3 to
T2 dependence of low-
T Cmag accompanying a low-
T shift of magnetic entropy. These results may suggest a gradual change from AF to spin-liquid like states with an increase in
x.
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Shonosuke Ohta
2009 Volume 78 Issue 1 Pages
013605
Published: January 15, 2009
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An abnormal and unsteady growth of an isotropic cluster in diffusion-limited aggregation (DLA) is observed in stability analyses. Macroscopic fluctuation due to the delay of transition from a dendritic tip to a tip-splitting growth induces the anisotropy of DLA. An asymptotic deformation factor ε
∞=0.0888 is obtained from large DLA clusters. A symmetric oval model proposed from the dual-stability growth of DLA gives an asymptotic fractal dimension of 1.7112 using ε
∞. The correspondence of this model to the box dimension is excellent.
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Nobuyuki Terasaki, Hidekazu Mukuda, Mitsuharu Yashima, Yoshio Kitaoka, ...
2009 Volume 78 Issue 1 Pages
013701
Published: January 15, 2009
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We report
57Fe-NMR studies on the oxygen-deficient iron (Fe)-based oxypnictide superconductor LaFeAsO
0.7 (
Tc=28 K) enriched by
57Fe isotope. In the superconducting state, the spin component of
57Fe-Knight shift decreases to almost zero at low temperatures, and the nuclear spin–lattice relaxation rate
57(1⁄
T1) exhibits a
T3-like dependence without the coherence peak just below
Tc, which provide firm evidence of the unconventional superconducting state formed by spin-singlet Cooper pairing. All these events below
Tc are consistently argued in terms of the extended s
±-wave pairing with a sign reversal of the order parameter among Fermi surfaces. In the normal state, we found the remarkable decrease in 1⁄
T1T upon cooling for both the Fe and As sites, which originates from the decrease in low-energy spectral weight of spin fluctuations over whole
q space upon cooling below room temperature. Such behavior has never been observed for other strongly correlated superconductors where an antiferromagnetic interaction plays a vital role in mediating the Cooper pairing.
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Yuta Hadano, Shouta Narazu, Marcos A. Avila, Takahiro Onimaru, Toshiro ...
2009 Volume 78 Issue 1 Pages
013702
Published: January 15, 2009
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We report transport, thermal, and magnetic measurements on single crystalline samples of FeGa
3 prepared by a Ga self flux method. The electrical resistivity and Hall coefficient at temperatures above 300 K display semiconducting behaviors with energy gaps of 0.47 and 0.54 eV, respectively, whose values agree with the calculated band gap. In the saturation range 100–260 K, the carrier mobility μ exhibits an unusual dependence on temperature; μ(
T)∝
T−5⁄2. The thermopower has a large negative minimum of −350 μV/K at 300 K. The diamagnetic susceptibility weakly depends on temperature, which confirms the absence of localized magnetic moments. The
T-linear coefficient of the specific heat is 0.03 mJ/(K
2·mol), being two orders of magnitude smaller than that reported for Fe-based Kondo semiconductors FeSi and FeSb
2.
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Yasutami Takada
2009 Volume 78 Issue 1 Pages
013703
Published: January 15, 2009
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Based on the model that was successfully applied to KC
8, RbC
8, and CsC
8 in 1982, we have calculated the superconducting transition temperature
Tc for CaC
6 and YbC
6 to find that the same model reproduces the observed
Tc in those compounds as well, indicating that it is a unified model for superconductivity in the graphite intercalation compounds with
Tc ranging over three orders of magnitude. Further enhancement of
Tc well beyond 10 K is also predicted.
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Hisashi Kondo, Tôru Moriya
2009 Volume 78 Issue 1 Pages
013704
Published: January 15, 2009
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Spin fluctuations (SF) and SF-mediated superconductivity (SC) in quasi-two-dimensional metals around the antiferrromagnetic (AF) quantum critical point (QCP) are investigated by using the self-consistent renormalization theory for SF and the strong coupling theory for SC. We introduce a parameter
y0 as a measure for the distance from the AFQCP which is approximately proportional to (
x−
xc),
x being the electron (e) or hole (h) doping concentration to the half-filled band and
xc being the value at the AFQCP. We present phase diagrams in the
T–
y0 plane including contour maps of the AF correlation length and AF and SC transition temperatures
TN and
Tc, respectively. The
Tc curve is dome-shaped with a maximum at around the AFQCP. The calculated one-electron spectral density shows a pseudogap in the high-density-of-states region near (π,0) below around a certain temperature
T* and gives a contour map at the Fermi energy reminiscent of the Fermi arc. These results are discussed in comparison with e- and h-doped high-
Tc cuprates.
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Reiji Kumai, Nao Takeshita, Toshimitsu Ito, Hijiri Kito, Akira Iyo, Hi ...
2009 Volume 78 Issue 1 Pages
013705
Published: January 15, 2009
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The atomic positions of the title oxypnictide compound under pressure were determined by Rietveld analysis of synchrotron X-ray diffraction data. Hydrostatic pressure has effects on the crystal structure in two points: (i) nearly isotropic compression of each of the Fe–As and Nd–O layers at the rate of ∼0.2%/GPa and (ii) outstanding shrinkage of the interlayer spacing (defined as the distance between adjacent As and Nd planes in this paper) at the rate of ∼0.7%/GPa. Remarkable suppression of
Tc by hydrostatic pressure would originate from the change in the electronic structure caused by the modification of the crystal structure. The possible origins will be discussed.
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Takashi Yanagisawa, Mitake Miyazaki, Kunihiko Yamaji
2009 Volume 78 Issue 1 Pages
013706
Published: January 15, 2009
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Numerical studies of the two-dimensional d–p model using the Gutzwiller ansatz have exhibited the incommensurate antiferromagnetic state coexisting with superconductivity in the under- and lightly doped regions. Our results are based on the variational Monte Carlo method for the three-band Hubbard model with d and p orbitals. We obtained the finite superconducting condensation energy for the coexistent sate at the doping rate
x=1⁄8, 1/12, and 1/16, up to the systems of 256 unit cells with 768 atoms (oxygen and copper atoms). The phase diagram for the hole-doped case is consistent with recent results reported for layered high temperature cuprates.
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Shinichi Itoh, Tsuneyoshi Nakayama, Ryoichi Kajimoto, Mark A. Adams
2009 Volume 78 Issue 1 Pages
013707
Published: January 15, 2009
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The dynamic structure factors
S(
q,ω) of an ideal percolating network, the three-dimensional (3
d) dilute Heisenberg antiferromagnet RbMn
0.4Mg
0.6F
3, obtained from high resoluton (Δ
E=17.5 μeV) inelastic neutron scattering (INS) experiments are analyzed for the first time within the framework of the single-length-scaling postulate (SLSP). The analysis confirms the validity of the SLSP and is also used to extract the values of the key exponents governing the spin dynamics, the dynamic exponent (
zAF=
Df⁄\\ ilde
dAF) being 2.5±0.1 and the spectral dimension \\ ilde
dAF for antiferromagnetic (AFM) fractons taking a value of unity.
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Clifford W. Hicks, Thomas M. Lippman, Martin E. Huber, Zhi-An Ren, Jie ...
2009 Volume 78 Issue 1 Pages
013708
Published: January 15, 2009
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Identifying the symmetry of the superconducting order parameter in the recently-discovered ferro-oxypnictide family of superconductors,
RFeAsO
1−xF
y, where
R is a rare earth, is a high priority. Many of the proposed order parameters have internal π phase shifts, like the
d-wave order found in the cuprates, which would result in direction-dependent phase shifts in tunnelling. In dense polycrystalline samples, these phase shifts in turn would result in spontaneous orbital currents and magnetization in the superconducting state. We perform scanning SQUID microscopy on a dense polycrystalline sample of NdFeAsO
0.94F
0.06 with
Tc=48 K and find no such spontaneous currents, ruling out many of the proposed order parameters.
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Hisashi Kotegawa, Hitoshi Sugawara, Hideki Tou
2009 Volume 78 Issue 1 Pages
013709
Published: January 15, 2009
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We report resistivity measurement under pressure in single crystals of SrFe
2As
2, which is one of the parent materials of Fe-based superconductors. The structural and antiferromagnetic (AFM) transition of
T0=198 K at ambient pressure is suppressed under pressure, and the ordered phase disappears above
Pc∼3.6–3.7 GPa. Superconductivity with a sharp transition appears accompanied by the suppression of the AFM state.
Tc exhibits a maximum of 34.1 K, which is realized close to the phase boundary at
Pc. This
Tc is the highest among those of the stoichiometric Fe-based superconductors.
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Shin-ichi Kimura, Takuya Iizuka, Yong-seung Kwon
2009 Volume 78 Issue 1 Pages
013710
Published: January 15, 2009
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We have demonstrated that the middle-infrared (mid-IR) peaks in the optical conductivity spectra of Ce
X3 (
X=Pd, Sn, In) can be explained by first-principle band structure calculation with the spin–orbit interaction. The mid-IR peak shapes in these materials are not identical to one another: CePd
3, CeSn
3, and CeIn
3 have a triple-peak structure, a double-peak structure, and a broad single-peak structure, respectively. These peaks can be theoretically explained by the optical transition from the occupied state to the spin–orbit splitted Ce 4
f state. This result indicates that the mid-IR peaks originate from the simple band picture with the Ce 4
f state near the Fermi level, not from the conventional
cf hybridization gap based on the periodic Anderson model.
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Fanlong Ning, Kanagasingham Ahilan, Takashi Imai, Athena S. Sefat, Ron ...
2009 Volume 78 Issue 1 Pages
013711
Published: January 15, 2009
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We report a systematic investigation of Ba(Fe
1−xCo
x)
2As
2 based on transport and
75As NMR measurements, and establish the electronic phase diagram. We demonstrate that doping progressively suppresses the uniform spin susceptibility and low frequency spin fluctuations. The optimum superconducting phase emerges at
xc\\simeq0.08 when the tendency toward spin ordering completely diminishes. Our findings point toward the presence of a quantum critical point near
xc between the SDW (spin density wave) and superconducting phases.
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Hiroshi Ueda, Tomotoshi Nishino
2009 Volume 78 Issue 1 Pages
014001
Published: January 15, 2009
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A group of non-uniform quantum lattice Hamiltonians in one dimension is introduced, which is related to the hyperbolic (1+1)-dimensional space. The Hamiltonians contain only nearest neighbor interactions whose strength is proportional to cosh
jλ, where
j is the lattice index and where λ≥0 is a deformation parameter. In the limit λ→0 the Hamiltonians become uniform. Spacial translation of the deformed Hamiltonians is induced by the corner Hamiltonians. As a simple example, we investigate the ground state of the deformed
S=1⁄2 Heisenberg spin chain by use of the density matrix renormalization group (DMRG) method. It is shown that the ground state is dimerized when λ is finite. Spin correlation function show exponential decay, and the boundary effect decreases with increasing λ.
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Yusuke Tomita
2009 Volume 78 Issue 1 Pages
014002
Published: January 15, 2009
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Recently, Fukui and Todo have proposed a new effective Monte Carlo algorithm for long-range interacting systems. Using the algorithm with the nonequilibrium relaxation method, we investigated long-range interacting one-dimensional Ising models both ferromagnetic and antiferromagnetic with the nearest-neighbor ferromagnetic interaction. For the antiferromagnetic model, we found the systems are paramagnetic at finite temperatures.
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Hiroki Nakano, Akira Terai
2009 Volume 78 Issue 1 Pages
014003
Published: January 15, 2009
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We propose two methods of estimating a systematic error in extrapolation to the infinite-size limit in the study of measuring the Haldane gaps of the one-dimensional Heisenberg antiferromagnet with the integer spin up to
S=5. The finite-size gaps obtained by numerical diagonalizations based on Lanczos algorithm are presented for sizes that have not previously been reported. The changes of boundary conditions are also examined. We successfully demonstrate that our methods of extrapolation work well. The Haldane gap for
S=1 is estimated to be 0.4104789±0.0000013. We successfully obtain the gaps up to
S=5, which make us confirm the asymptotic formula of the Haldane gap in
S→∞.
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Ejaz Ahmed, Miwako Takahashi, Hiroshi Iwasaki, Ken-ichi Ohshima
2009 Volume 78 Issue 1 Pages
014601
Published: January 15, 2009
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We investigated the ordering behavior of ternary CuMPt
6 alloys with M=Ti, V, Cr, Mn, Fe, Co, and Ni by high-temperature polycrystalline X-ray diffraction. The alloys undergo a phase transition from the fcc disordered state to the Cu
3Au-type ordered state, except for the alloy with M=Ni, in which only short-range order forms. The transition temperature
Tc is highest (1593 K) for M=Ti and decreases almost monotonically with increasing atomic number to 1153 K for M=Co. The observed dependence of ordering tendency on the atomic number of M is discussed in the light of the theory of ordering in transition-metal alloys and its significance for the study of ordering in ternary alloys.
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Carlos Alberto Lamas
2009 Volume 78 Issue 1 Pages
014602
Published: January 15, 2009
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The two-dimensional Hubbard model on the square lattice is studied in the presence of lattice distortions in the adiabatic approximation. The self energy is computed within perturbation theory up to second order, which provides a way for studying the quasiparticle dispersion. We compute numerically the second order contribution to the self-energy using a standard fast Fourier transform algorithm for finite sizes system. The stability of the lattice distortions is investigated and a schematic phase diagram is drawn. The Fermi surface is analyzed for densities close to half filling, the presence of lattice distortions changes some spectral properties of the model and gives an anisotropic interacting Fermi surface. The spectral function is calculated along several lines in momentum space and the renormalized quasiparticle dispersion is obtained. The behavior of the density of states is shown for different values of the intrasite repulsion
U in the different phases.
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Naoki Kikugawa, Luis Balicas, Andrew Peter Mackenzie
2009 Volume 78 Issue 1 Pages
014701
Published: January 15, 2009
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We report the successful growth of single crystals of the perovskite ruthenate CaRuO
3 by a floating-zone method, and characterization of their physical properties by x-ray diffraction, electrical resistivity, magnetic susceptibility, and specific heat. Although the system is strongly correlated, with an electronic specific heat coefficient of approximately 80 mJ/(mol K
2 Ru), the physical properties are nearly isotropic, reflecting the almost cubic crystal structure. No obvious phase transitions are observed down to 0.12 K, in contrast to observations on other metallic ruthenates with the Ruddlesden–Popper type layered perovskite structure
An+1Ru
nO
3n+1 such as Sr
2RuO
4, Sr
3Ru
2O
7, and Ca
3Ru
2O
7.
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Junya Otsuki, Hiroaki Kusunose, Yoshio Kuramoto
2009 Volume 78 Issue 1 Pages
014702
Published: January 15, 2009
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A Green-function formalism for the Kondo lattice model is presented, which is designed to be combined with dynamical mean-field theory. Using Wick’s theorem only for conduction electrons, dynamical quantities are represented in terms of the
t-matrix and its two-particle generalizations. By taking the high-frequency limit of the
t-matrix with respect to a part of the fermion frequencies, one obtains dynamical correlation functions of localized moments. Explicit examples of calculation steps are provided using the continuous-time quantum Monte Carlo method.
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Yuh-ichi Iyama, Fumitaka Matsubara
2009 Volume 78 Issue 1 Pages
014703
Published: January 15, 2009
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We developed a genetic algorithm (GA) in the Heisenberg model that combines a triadic crossover and a parameter-free genetic algorithm. Using the algorithm, we examined the ground-state stiffness of the ±
J Heisenberg model in three dimensions up to a moderate size range. Results showed the stiffness constant of θ=0 in the periodic–antiperiodic boundary condition method and that of θ∼0.62 in the open-boundary-twist method. We considered the origin of the difference in θ between the two methods and suggested that both results show the same thing: the ground state of the open system is stable against a weak perturbation.
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Yoshihiro Ishibashi, Makoto Iwata
2009 Volume 78 Issue 1 Pages
014704
Published: January 15, 2009
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The interaction between the protons on the nearby hydrogen bonds in NH
4H
2PO
4 (ADP)-type crystals, called the Ishibashi interaction, was analyzed to derive theoretically, i.e., not in an
ad hoc way, the effective dipole–dipole interaction between PO
4 radicals, which plays a substantial role in phase transitions. It turns out that at low temperatures the ADP-type antiferroelectric phase is stabilized if the Ishibashi interaction is repulsive, while the monoclinic ferroelectric phase is stabilized otherwise.
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Hidekazu Mukuda, Sachihiro Nishide, Atsushi Harada, Kaori Iwasaki, Mam ...
2009 Volume 78 Issue 1 Pages
014705
Published: January 15, 2009
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We report on novel superconducting characteristics of the heavy fermion (HF) superconductor CePt
3Si without inversion symmetry through
195Pt-NMR study on a single crystal with
Tc=0.46 K that is lower than
Tc∼0.75 K for polycrystals. We show that the intrinsic superconducting characteristics inherent to CePt
3Si can be understood in terms of the unconventional strong-coupling state with a line–node gap below
Tc=0.46 K. The mystery about the sample dependence of
Tc is explained by the fact that more or less polycrystals and single crystals inevitably contain some disordered domains, which exhibit a conventional BCS
s-wave superconductivity (SC) below 0.8 K. In contrast, the Néel temperature
TN∼2.2 K is present regardless of the quality of samples, revealing that the Fermi surface responsible for SC differ from that for the antiferromagnetic order. These unusual characteristics of CePt
3Si can be also described by a multiband model; in the homogeneous domains, the coherent HF bands are responsible for the unconventional SC, whereas in the disordered domains the conduction bands existing commonly in LaPt
3Si may be responsible for the conventional
s-wave SC. We remark that some impurity scatterings in the disordered domains break up the 4
f-electrons-derived coherent bands but not others. In this context, the small peak in 1⁄
T1 just below
Tc reported before [Yogi
et al. (2004)] is not due to a two-component order parameter composed of spin-singlet and spin-triplet Cooper pairing states, but due to the contamination of the disorder domains which are in the
s-wave SC state.
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Tien Quang Nguyen, Mary Clare Sison Escaño, Reiko Tanaka, Hiros ...
2009 Volume 78 Issue 1 Pages
014706
Published: January 15, 2009
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The adsorption of NO on various metal tape-porphyrins (Mn, Fe, and Co) is studied using first-principles calculations based on density functional theory (DFT). In this work we discuss the geometric structure and electronic properties of metal tape-porphyrins and the effect of the adsorption of NO on their properties. The results show that metal atoms protrude from the porphyrin plane toward the NO molecule. At the stable position, the variation of the metal–N–O angle is in the order: Co–N–O (123°) < Fe–N–O (148°) < Mn–N–O (180°). The N–O bond length in the metal tape-porphyrins is slightly longer than that of the isolated NO molecule. These results are consistent with other DFT calculations and experimental results. We also found that the binding energy of NO with metal porphyrins increases in the order CoTP–NO (1.718 eV) < FeTP–NO (1.719 eV) < MnTP–NO (1.736 eV). As regards the electronic properties, there is a metal–insulator transition in FeTP–NO. For CoTP–NO and MnTP–NO, we found that CoTP shows insulator-like behavior while MnTP is metallic. After interaction with NO, CoTP still shows insulator-like behavior but MnTP has reduced conductance. We attribute the changes in the geometric and electronic structures to the interactions involving the 3
d orbitals of the metal atoms and the π
* orbital of NO. Specifically, for MnTP, the change in the electronic properties is attributed to the strong hybridization of the
dxz and
dyz orbitals of the Mn atom with the π
* orbital of NO. For CoTP, the hybridization of the
dz2 orbital of the Co atom with the π
* orbitals of NO plays the key role in the NO–cobalt tape-porphyrin interaction.
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Mitake Miyazaki, Chisa Hotta, Shin Miyahara, Keisuke Matsuda, Nobuo Fu ...
2009 Volume 78 Issue 1 Pages
014707
Published: January 15, 2009
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We analyze a model of spinless fermions on a triangular lattice at half-filling interacting via strong nearest-neighbor repulsive interactions,
V, using the variational Monte Carlo simulation technique. The comparative analysis of two different types of variational wave functions with and without translational symmetry breaking reveals that the system undergoes a phase transition at
Vc⁄
t\\gtrsim12, accompanied by the reconstruction of the Fermi surface. The existence of three-sublattice long-range order in the strong coupling region is confirmed by the finite-size scaling analysis. The ordered phase shows characteristics expected for a so called “pinball liquid” state, which has the spontaneous separation of fermionic degrees of freedom into coexisting Wigner crystal-like charge order (pin) and a metal (ball). The pins are fixed in order to maximize the kinetic energy gain of balls which move almost freely. We also find the charge-density-wave-like state only for the symmetry broken wave functions at
V<
Vc, which, however, possibly remains as a short-range order in the bulk limit, and is distinguished from the pinball liquid characterized by the large value of
Vc⁄
t.
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Shin-ichi Hikino, Michiyasu Mori, Saburo Takahashi, Sadamichi Maekawa
2009 Volume 78 Issue 1 Pages
014708
Published: January 15, 2009
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The ac Josephson effect in a ferromagnetic Josephson junction, which is composed of two superconductors separated by a ferromagnetic metal (FM), is studied by a tunneling Hamiltonian and Green’s function method. We obtain two types of superconducting phase dependent currents, i.e., Josephson current and quasiparticle-pair-interference current (QPIC). These currents change their signs with thickness of the FM layer due to the 0–π transition characteristic to the ferromagnetic Josephson junction. As a function of applied voltage, the Josephson critical current shows a logarithmic divergence called the Riedel peak at the gap voltage, while the QPIC shows a discontinuous jump. The Riedel peak reverses due to the 0–π transition and disappears near the 0–π transition point. The discontinuous jump in the QPIC also represents similar behaviors to the Riedel peak. These results are in contrast to the conventional ones.
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Takeshi Mito, Satoru Tomisawa, Shinji Wada, Hisatomo Harima, Kenjiro H ...
2009 Volume 78 Issue 1 Pages
014709
Published: January 15, 2009
Released on J-STAGE: December 28, 2011
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The phase transition at
T∗=80 K in YbAl
3C
3 has been studied by
27Al nuclear quadrupole resonance (NQR) measurement and nuclear magnetic resonance (NMR) measurement up to 30 T. The NQR and NMR spectra reveal clear anomalies just below
T∗, which provides the first microscopic evidence for symmetry lowering in the low-temperature phase below
T∗. The transition is characterized by marked changes in the
27Al-NQR frequencies ν
Q’s without significant changes in the lattice parameters. The field dependence of the transition is also investigated. The NMR line exhibits field-induced rapid broadening below
T∗, which almost vanishes in zero field. Moreover, we found that
T∗ increases by 10 K at 30 T. These unique magnetic properties are consistent with the scheme that the microscopic mechanism underlying the phase transition involves Yb-4
f electrons rather than the scheme of a simple structural phase transition.
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Tsutomu Fujimoto, Toshiki Hayashi, Toyonari Sugimoto, Harukazu Yoshino ...
2009 Volume 78 Issue 1 Pages
014710
Published: January 15, 2009
Released on J-STAGE: December 28, 2011
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Electronic properties of the π–d system (EDT-DSDTFVSDS)
2FeBr
4 are investigated under high pressure up to 6.5 GPa, where EDT-DSDTFVSDS = ethylenedithiodiselenadithiafulvalenothioquinone-1,3-diselenolemethide. In order to extract the π–d interaction, the nonmagnetic anion analogue salt (EDT-DSDTFVSDS)
2GaBr
4 is also investigated for comparison. Both salts show metallic electrical resistivity at high temperature, but exhibit insulating behaviors in two pressure regions, in the low-pressure region, i.e., [
P<3.5 GPa (2.0 GPa)] for the FeBr
4 (GaBr
4) salts, as well as in the high-pressure region, i.e., (
P>3.0 GPa) for both salts. Below 3.5 GPa, the low-pressure insulating state of the FeBr
4 salt is enhanced by the π–d interaction. Whereas, the high-pressure insulating state of the FeBr
4 salt is not enhanced above 3.5 GPa. On the other hand, the π–d interaction may affect the nonmetallic behavior of the resistance above 200 K in the FeBr
4 salt owing to the scattering of π electrons from thermally fluctuating d spins.
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Hidetsugu Sakaguchi
2009 Volume 78 Issue 1 Pages
014801
Published: January 15, 2009
Released on J-STAGE: December 28, 2011
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A high activity of reactions can be confined in a model cell with a semipermeable membrane in the Schlögl model. It is interpreted as a model of primitive metabolism in a cell. We study two generalized models to understand the creation of primitive cell systems conceptually from the view point of the nonlinear–nonequilibrium physics. In the first model, a single-cell system with a highly active state confined by a semipermeable membrane is spontaneously created from an inactive homogeneous state by a stochastic jump process. In the second model, many cell structures are reproduced from a single cell, and a multicellular system is created.
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Masatoshi Misono, Tuyoshi Todo, Kenji Miyakawa
2009 Volume 78 Issue 1 Pages
014802
Published: January 15, 2009
Released on J-STAGE: December 28, 2011
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We study the coherence resonance in a Schmitt-trigger inverter with a delayed feedback loop. The output of the system is analyzed changing the input noise amplitude and the delay time of the feedback loop. The regularity of the output shows resonance-like dependence on the input noise amplitude. At the optimum input noise amplitude, the system outputs well-regulated rectangular wave, and corresponding peaks in the output spectrum become large and sharp. This optimization of the system is accomplished when the period of the output rectangular wave almost coincides with the feedback delay time.
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Azhar Iqbal, Derek Abbott
2009 Volume 78 Issue 1 Pages
014803
Published: January 15, 2009
Released on J-STAGE: December 28, 2011
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A quantum version of the matching pennies (MP) game is proposed that is played using an Einstein–Podolsky–Rosen–Bohm (EPR–Bohm) setting. We construct the quantum game without using state vectors, while considering only the quantum mechanical joint probabilities relevant to the EPR–Bohm setting. We embed the classical game within the quantum game such that the classical MP game results when the quantum mechanical joint probabilities become factorizable. We report new Nash equilibria in the quantum MP game that emerge when the quantum mechanical joint probabilities maximally violate the Clauser–Horne–Shimony–Holt form of Bell’s inequality.
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Hiroshi Morita, Simone Plog, Tadashi Kajiya, Masao Doi
2009 Volume 78 Issue 1 Pages
014804
Published: January 15, 2009
Released on J-STAGE: December 28, 2011
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The sliding of a droplet of polystyrene solution on an inclined glass substrate is studied experimentally. The droplet shape and the sliding velocity are measured with varying the inclination angle, the droplet volume and the polymer concentration. We found that although the sliding behavior of polymer solution droplet is similar to those reported previously for the Newtonian fluid (silicone oil), clear difference is seen when the results are compared in terms of the relation between the capillary number and the Bond number. This result suggests that the slippage of polymer solution in the depletion layer at the solid boundary is important in the sliding behavior.
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Wei-Guo Jin, Hiroki Nakai, Masayuki Kawamura, Tatsuya Minowa
2009 Volume 78 Issue 1 Pages
015001
Published: January 15, 2009
Released on J-STAGE: December 28, 2011
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Takuji Nomura, Kosaku Yamada
2009 Volume 78 Issue 1 Pages
018001
Published: January 15, 2009
Released on J-STAGE: December 28, 2011
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Yasuhiro Tanaka, Kenji Yonemitsu
2009 Volume 78 Issue 1 Pages
018002
Published: January 15, 2009
Released on J-STAGE: December 28, 2011
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