巻号一覧
77 巻, 1 号
選択された号の論文の32件中1～32を表示しています
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Kenji Harada, Yuto Kuge2008 年 77 巻 1 号 p. 013001
発行日: 2008/01/15
公開日: 2011/12/28
ジャーナル 認証ありThe dynamics of samples in the continuous-imaginary-time quantum world-line Monte Carlo simulations with extended ensembles are investigated. In the case of a conventional flat ensemble on the one-dimensional quantum S=1 bi-quadratic model, the asymmetric behavior of Monte Carlo samples appears in the diffusion process in the space of the number of vertices. We prove that a local diffusivity is asymptotically proportional to the number of vertices, and we demonstrate the asymmetric behavior in the flat ensemble case. On the basis of the asymptotic form, we propose the weight of an optimal ensemble as 1⁄\\sqrtn, where n denotes the number of vertices in a sample. It is shown that the asymmetric behavior completely vanishes in the case of the proposed ensemble on the one-dimensional quantum S=1 bi-quadratic model.抄録全体を表示PDF形式でダウンロード (111K) -
Keiichi Yamamoto, Yoshiyuki Shibayama, Keiya Shirahama2008 年 77 巻 1 号 p. 013601
発行日: 2008/01/15
公開日: 2011/12/28
ジャーナル 認証ありWe have studied the liquid–solid (L–S) phase transition of 4He confined in nanoporous Gelsil glass that has interconnected nanopores of 2.5-nm diameter. The L–S boundary is determined by a series of measurements of pressure versus temperature along isochores and the rate of temperature change during slow cooling and warming in a semi-adiabatic condition. Below 1 K, the freezing pressure is elevated by 1.2 MPa from the bulk freezing pressure, and appears to be independent of temperature. The T-independent freezing pressure strongly suggests the existence of the localized Bose–Einstein condensation state.抄録全体を表示PDF形式でダウンロード (282K) -
Yusuke Kato, Hiroshi Nishiwaki, Akitake Fujita2008 年 77 巻 1 号 p. 013602
発行日: 2008/01/15
公開日: 2011/12/28
ジャーナル 認証ありWe clarify the origin of anomalous tunneling [Kagan et al.: Phys. Rev. Lett. 90 (2003) 130402] i.e., the perfect transmission at low energy limit of tunneling of phonon excitations across the potential barrier separating two Bose condensates. The perfect transmission is a consequence of the coincidence of the wave function of the excited state at low energy limit and the macroscopic wave function of the condensate. We show that the perfect transmission at low energy occurs even at finite temperatures within the scheme of Popov approximation.抄録全体を表示PDF形式でダウンロード (97K) -
Fumiko Yamada, Toshio Ono, Hidekazu Tanaka, Grégoire Misguich, ...2008 年 77 巻 1 号 p. 013701
発行日: 2008/01/15
公開日: 2011/12/28
ジャーナル 認証ありMagnetization measurements were performed to investigate the critical behavior of the field-induced magnetic ordering in gapped spin system TlCuCl3. The critical density of the magnons was obtained as a function of temperature and the magnon-magnon interaction constant was evaluated. The experimental phase boundary for T<5 K agrees almost perfectly with the magnon Bose–Einstein condensation (BEC) theory based on the Hartree–Fock approximation with realistic dispersion relations. The phase boundary can be described by the power law [HN(T)−Hc]∝Tφ. With decreasing fitting temperature range, the critical exponent φ decreases and converges at φBEC=3⁄2 predicted by the magnon BEC theory.抄録全体を表示PDF形式でダウンロード (367K) -
Masaru Onoda, Andrei S. Mishchenko, Naoto Nagaosa2008 年 77 巻 1 号 p. 013702
発行日: 2008/01/15
公開日: 2011/12/28
ジャーナル 認証ありThe spin wave dynamics in metallic ferromagnet is studied theoretically taking into account the relativistic spin–orbit interaction. It is found that its quantum dynamics is seriously influenced by the band crossings near the Fermi energy, and sometimes the direction of the precession, i.e., the handedness, can be reversed from that expected from the commutation relation of the spin components. Namely, the left-handed spin wave excitation can be realized in systems with the spin–orbit interaction.抄録全体を表示PDF形式でダウンロード (132K) -
Zhangzhen He, Yutaka Ueda2008 年 77 巻 1 号 p. 013703
発行日: 2008/01/15
公開日: 2011/12/28
ジャーナル 認証ありMagnetic ground state of SrNi2V2O8 has been investigated by many authors [Phys. Rev. Lett. 83 (1999) 632; Phys. Rev. B 62 (2000) 8921; and Phys. Rev. B 73 (2006) 012407], showing the different conclusions of which SrNi2V2O8 falls into an ordered state or a spin-liquid state. In this study, we observed a quantum phase transition of a spin-liquid state to an ordered state in SrNi2V2O8 by a minor substitution of Ca2+ ions. Our experimental results provide concrete evidence that SrNi2V2O8 is likely in a disordered ground state, which is close to the phase boundary between the spin-liquid and the Ising-like Néel ordered state on the Sakai–Takahashi phase diagram.抄録全体を表示PDF形式でダウンロード (363K) -
Hidenori Kubo, Kazuko Zenmyo, Masahiko Tokita, Tatsuichi Hamasaki, Mas ...2008 年 77 巻 1 号 p. 013704
発行日: 2008/01/15
公開日: 2011/12/28
ジャーナル 認証ありNMR studies of a geometrically frustrated system, Co2Cl(OH)3, are carried out at low temperature. The NMR results of 59Co and 1H nuclei show that long-range ordered ferromagnetic moments on the triangular lattice plane coexist microscopically with disordered moments on the kagome lattice plane. The moment direction is not ordered. Although the disordered moments freeze within the NMR observation time (10−4 s) at low temperature, the frozen moments begin to fluctuate with increasing temperature. Up to 4.2 K (0.4TC), the magnitude of the ferromagnetically ordered moments is independent of temperature.抄録全体を表示PDF形式でダウンロード (122K) -
Mitsuru Saito, Kouji Taniguchi, Taka-hisa Arima2008 年 77 巻 1 号 p. 013705
発行日: 2008/01/15
公開日: 2011/12/28
ジャーナル 認証ありAlthough it has been well known that materials in which both space inversion and time reversal symmetries are broken can host optical magneto-electric effect, i.e., change in optical constants with the reversal of propagating direction of light, the largest change in absorption ever reported on this effect was 0.2%. Here we show that optical absorption in noncentrosymmetric weak ferromagnetic material CuB2O4 changes by more than 100% with reversal of a low magnetic field of 300 Oe. The gigantic optical magneto-electric effect is ascribed to the canted antiferromagnetic spin ordering of square-coordinated Cu2+ sites, where the local inversion is slightly broken.抄録全体を表示PDF形式でダウンロード (1267K) -
Akio Kotani2008 年 77 巻 1 号 p. 013706
発行日: 2008/01/15
公開日: 2011/12/28
ジャーナル 認証ありTheoretical study is made, with an extended single impurity Anderson model, for the spectra of X-ray magnetic circular dichroism (XMCD) at Ce L2,3 edges of trivalence, weakly mixed valence and strongly mixed valence Ce compounds under external magnetic field. Recent experimental results for CePd3 are well explained. The present theory gives a framework to understand a variety of XMCD behavior of various kinds of ferromagnetic Ce compounds in a unified fashion.抄録全体を表示PDF形式でダウンロード (174K) -
Xiao-Long Zhu, Xian-Wu Zou, Zhi-Gang Shao, Sheng-You Huang, Jian-Ping ...2008 年 77 巻 1 号 p. 014001
発行日: 2008/01/15
公開日: 2011/12/28
ジャーナル 認証ありMany structure parameters have been suggested to predict the synchronizability of complex networks. They were qualitatively suitable for certain networks but failed for others. Based on the coupled oscillator model, we find that the homogeneity of load distribution determines the synchronizability of complex networks, and the standard deviation of edge betweenness centrality is coincident with synchronizability for various complex networks. These results suggest that in order for a network to hence to synchronize more effectively, the load distribution must be more homogeneous.抄録全体を表示PDF形式でダウンロード (239K) -
Yohsuke Murase, Nobuyasu Ito2008 年 77 巻 1 号 p. 014002
発行日: 2008/01/15
公開日: 2011/12/28
ジャーナル 認証ありValues of dynamic critical exponents are numerically estimated for various models with the nonequilibrium relaxation method to test the dynamic universality hypothesis. The dynamics used here are single-spin update with Metropolis-type transition probabities. The estimated values of nonequilibrium relaxation exponent of magnetization λm (=β⁄zν) of Ising models on bcc and fcc lattices are estimated to be 0.251(3) and 0.252(3), respectively, which are consistent with the value of the model on simple-cubic lattice, 0.250(2). The dynamic critical exponents of three-states Potts models on square, honeycomb and triangular lattices are also estimated to be 2.193(5), 2.198(4), and 2.199(3), respectively. They are consistent within the error bars. It is also confirmed that Ising models with regularly modulated coupling constants on square lattice have the same dynamic critical exponents with the uniformly ferromagnetic Ising model.抄録全体を表示PDF形式でダウンロード (204K) -
Chunli Chen, Shoujun Huang, Jin E. Zhang2008 年 77 巻 1 号 p. 014003
発行日: 2008/01/15
公開日: 2011/12/28
ジャーナル 認証ありIn this paper, we consider the head-on collision between two solitary waves of Nwogu’s Boussinesq equation which contains one parameter c that is related to that the horizontal velocities at what level are chosen as the horizontal velocity variables. We apply the perturbation method to derive an approximate solution to this equation and investigate the mechanics of the head-on collision. The impacts of the parameter c on the phase shifts and the maximum run-up amplitude of two colliding waves are studied. Comparison between our results and that of the integrable classical Boussinesq equation is also given.抄録全体を表示PDF形式でダウンロード (298K) -
Shigeru Taniguchi, Masashi Nakamura, Masaru Sugiyama, Masaharu Isobe, ...2008 年 77 巻 1 号 p. 014004
発行日: 2008/01/15
公開日: 2011/12/28
ジャーナル 認証ありMolecular dynamics simulation data on stationary heat conduction in a one-dimensional binary hard-point gas are studied: We estimate the validity range of the local equilibrium assumption explicitly. The temperature profiles with the temperature jumps at the boundaries are analyzed consistently by a phenomenological theory beyond the local equilibrium assumption (extended thermodynamics). The agreement between the numerical result of the temperature profiles and its theoretical prediction is fairly well. The heat conductivity is analyzed in two limiting cases: We find that the exponent, which characterizes the divergence of the heat conductivity in a thermodynamic limit, depends on the mass ratio of two different constituent particles. We also find a power law relation between the heat conductivity and the mass ratio in a limit to the system where energy transport is in a ballistic mode.抄録全体を表示PDF形式でダウンロード (253K) -
Masanori Dozono, Tomotsugu Wakasa, Ema Ihara, Shun Asaji, Kunihiro Fuj ...2008 年 77 巻 1 号 p. 014201
発行日: 2008/01/15
公開日: 2011/12/28
ジャーナル 認証ありA complete set of polarization transfer observables has been measured for the 12C(p,n) reaction at Tp=296 MeV and θlab=0°. The measured polarization transfer observables indicate that the spin–dipole resonance at Ex\\simeq7 MeV has greater 2− strength than 1− strength, which is consistent with recent experimental and theoretical studies. The total spin transfer Σ(0°) deduced from the polarization transfer observables indicates a predominance of the spin-flip strength in the continuum. The exchange tensor interaction at a large momentum transfer of Q\\simeq3.6 fm−1 is discussed.抄録全体を表示PDF形式でダウンロード (199K) -
Hongming Weng, Taisuke Ozaki, Kiyoyuki Terakura2008 年 77 巻 1 号 p. 014301
発行日: 2008/01/15
公開日: 2011/12/28
ジャーナル 認証ありThe mechanism of ferromagnetism stability in sandwich clusters Vn(C6H6)n+1 has been studied by first-principles calculation and model analysis. It is found that each of the three types of bonds between V and benzene (Bz) plays different roles. V 3dz2 orbital, extending along the molecular axis, is weakly hybridized with Bz’s HOMO−1 orbital to form the σ-bond. It is quite localized and singly occupied, which contributes 1 μB to the magnetic moment but little to the magnetic coupling between neighboring V magnetic moments. The in-plane dx2−y2, dxy orbitals are hybridized with the LUMO of Bz and constitute the δ-bond. This hybridization is medium and crucial to the magnetic coupling though the δ states have no net contribution to the total magnetic moment. dxz, dyz, and HOMO of Bz form a quite strong π-bond to hold the molecular structure but they are inactive in magnetism because their energy levels are far away from the Fermi level. Based on the results of first-principles calculation, we point out that the ferromagnetism stability is closely related with the mechanism proposed by Kanamori and Terakura [J. Phys. Soc. Jpn. 70 (2001) 1433]. However, the presence of edge Bzs in the cluster introduces an important modification and suppresses significantly the ferromagnetism stability. A simple model is constructed to explain the essence of the physical picture.抄録全体を表示PDF形式でダウンロード (758K) -
Bhim P. Kafle, Hideki Katayanagi, Md. Serajul I. Prodhan, Hajime Yagi, ...2008 年 77 巻 1 号 p. 014302
発行日: 2008/01/15
公開日: 2011/12/28
ジャーナル 認証ありThe absolute total photoionization cross section σabs,I of gaseous C60 is measured in the photon energy hν range from 25 to 120 eV by photoionization mass spectrometry with synchrotron radiation. The absolute detection efficiencies of photoions in different charge states are evaluated. The present σabs,I curve is combined with the photoabsorption cross section curves of C60 at hν=3.5–26 eV in the literature, after appropriate alterations of the vapor pressure are taken into account. The oscillator strengths are computed from the composite curve to be 178.5 and 230.5 for the hν ranges from 3.5 to 40.8 eV and from 3.5 to 119 eV, respectively. These oscillator strengths agree well with those expected from the Thomas–Kuhn–Reiche sum rule and 60 times the photoabsorption cross section of a carbon atom. Moreover, the present σabs,I curve behaves similarly to the relative photoionization cross section curve reported by Reinköster et al.抄録全体を表示PDF形式でダウンロード (214K) -
Seiya Nishimura, Masatoshi Yagi, Sanae-I. Itoh, Kimitaka Itoh2008 年 77 巻 1 号 p. 014501
発行日: 2008/01/15
公開日: 2011/12/28
ジャーナル 認証ありThe nonlinear simulation of the collisional drift-tearing mode is performed using a reduced two-fluid model, and the characteristics of poloidal flow generated by the drift-tearing mode is investigated. It is found that poloidal flow extends to the outside of magnetic islands. It is also found that ion viscosity is an important parameter for determining the pattern of poloidal flow.抄録全体を表示PDF形式でダウンロード (588K) -
Takuya Kumagai, Akira Tamura2008 年 77 巻 1 号 p. 014601
発行日: 2008/01/15
公開日: 2011/12/28
ジャーナル 認証ありWe determined the stationary states of an electron confined in an equilateral triangular quantum corral by the superposition of electron waves undergoing successive reflections at three barrier walls. By using wave functions and eigenenergies, we analyzed scanning tunneling microscopy (STM) images and scanning tunneling spectra for the quantum corral. Our results are consistent with experimental STM images observed in the differential conductance mode (dI⁄dV) and scanning tunneling spectra. It is pointed out that the dI⁄dV image is not simply proportional to the surface local density of states but is greatly dependent on a filtering function.抄録全体を表示PDF形式でダウンロード (313K) -
Daisaku Kaneko, Masaru Kobayashi, Masaki Oshikawa, Hiroshi Morita, Mas ...2008 年 77 巻 1 号 p. 014602
発行日: 2008/01/15
公開日: 2011/12/28
ジャーナル 認証ありDirect observation is done for the thin lubrication layer in the friction between glass plate and soft elastomer using laser interference method. A poly(dimethylsiloxane) (PDMS) rubber having very flat surface was used as soft elastomer and water is used as lubricant. The surface of PDMS was modified by evaporation of a few dozen micron meters of Au layer in order to increase the reflectivity. It is observed that when the sliding velocity exceeded ca. 10−3 m/s, lubricant intrude into the dry zone from the outer edge, and that the decrease of the friction is due to the decrease of the dry area. This phenomenon is interpreted by the theory of Brochard et al.抄録全体を表示PDF形式でダウンロード (361K) -
Shin Yaginuma, Katsumi Nagaoka, Tadaaki Nagao, Gustav Bihlmayer, Yury ...2008 年 77 巻 1 号 p. 014701
発行日: 2008/01/15
公開日: 2011/12/28
ジャーナル 認証ありUsing scanning tunneling spectroscopy and first-principles calculations, we have studied the electronic structure of two different ultrathin bismuth films on a Si(111)-7×7 substrate; a hexagonal film (HEX film) having a bulklike (A7-like) structure and a film having a black-phosphorus-like structure (BP film). The HEX film is metallic because of spin–orbit (SO)-split surface-state bands lying inside the projected bulk band gap near the Fermi level. Another SO-split surface state is also observed inside the SO gap. The BP film exhibits a significant reduction in metallicity in contrast to the HEX film. This is related to the formation of a very stable paired-layer structure, the mechanism of which is similar to that of the stabilization of semiconducting bulk black P. However, unlike bulk black P, a certain extent of metallicity still remains. This slight metallicity can be associated with buckling and strain in the BP film, which is analogous to the fact that shear angle distortion in bulk Bi is responsible for its semimetallicity.抄録全体を表示PDF形式でダウンロード (1032K) -
Satoshi Akutagawa, Takeyoshi Ohashi, Haruhisa Kitano, Atsutaka Maeda, ...2008 年 77 巻 1 号 p. 014702
発行日: 2008/01/15
公開日: 2011/12/28
ジャーナル 認証ありY2C3 is a superconductor whose Tc changes from 6 to 18 K depending on the synthesis conditions. Since its electronic properties were unknown, we performed the electrical-property study by measuring the microwave complex surface impedance, Zs, of Y2C3 for different Tc’s (13.9 and 15.5 K), and the resistivity and mean free path were determined in the normal state. We observed the typical behavior of a Drude metal in the Hagen–Rubens limit (ρ1>>ρ2) in the normal state. We succeeded in observing the occurrence of superconductivity in the electrical property. Furthermore, we found that Y2C3 is a clean superconductor.抄録全体を表示PDF形式でダウンロード (228K) -
Yositake Takane2008 年 77 巻 1 号 p. 014703
発行日: 2008/01/15
公開日: 2011/12/28
ジャーナル 認証ありWe study the conductance of disordered wires with unitary symmetry focusing on the case in which m perfectly conducting channels are present due to the channel-number imbalance between two-propagating directions. Using the exact solution of the Dorokhov–Mello–Pereyra–Kumar (DMPK) equation for transmission eigenvalues, we obtain the average and second moment of the conductance in the long-wire regime. For comparison, we employ the three-edge Chalker–Coddington model as the simplest example of channel-number-imbalanced systems with m=1, and obtain the average and second moment of the conductance by using a supersymmetry approach. We show that the result for the Chalker–Coddington model is identical to that obtained from the DMPK equation.抄録全体を表示PDF形式でダウンロード (184K) -
Tsutomu Fujimoto, Syuma Yasuzuka, Keiichi Yokogawa, Harukazu Yoshino, ...2008 年 77 巻 1 号 p. 014704
発行日: 2008/01/15
公開日: 2011/12/28
ジャーナル 認証ありElectronic properties of the π–d system β-(EDT-DSDTFVSDS)2FeBr4 are investigated, where EDT-DSDTFVSDS = ethylenedithiodiselenadithiafulvalenothioquinone-1,3-diselenolemethide. Clear contrast between the FeBr4 salt and the nonmagnetic anion analogue salt, β-(EDT-DSDTFVSDS)2GaBr4, was observed in the electrical resistance and magnetoresistance (MR). The FeBr4 salt exhibits a giant negative MR of 85% at 0.7 K and 14 T. Furthermore, MR of the FeBr4 salt has a deep and sharp dip anomaly associated with the spin flop of the d spin at around 1.8 T below Néel temperature TNd=3.3 K. A model calculation, based on the assumption that antiferromagnetic arrangement of the d spins enhances an insulating state, qualitatively reproduced the experimental result. These results demonstrate the strong π–d interaction in the FeBr4 salt. Further, it is remarkable that in the higher angle of magnetic field from the easy axis, two anomalies associated with spin flop were observed. This behavior is neither explained by the conventional three-dimensional Ising nor XY models. The magnetic susceptibility of the FeBr4 salt obeys the Curie–Weiss law without a peak, which is characteristic of the usual low-dimensional antiferromagnet at higher temperature than Néel temperature.抄録全体を表示PDF形式でダウンロード (260K) -
Van An Dinh, Kazunori Sato, Hiroshi Katayama-Yoshida2008 年 77 巻 1 号 p. 014705
発行日: 2008/01/15
公開日: 2011/12/28
ジャーナル 認証ありBased on the first principle calculation, we propose a new class of high-Tc half-heusler ferromagnets NiMnZ (Z=Si, P, Ge, As). The structural and magnetic properties are investigated through the calculation of the electronic structure, phase stability, equilibrium lattice constant, magnetic exchange interaction Jij and Curie temperature Tc. It is found that all alloys show half-metallicity and ferromagnetism at temperatures much higher than room temperature in a wide range of lattice expansion (compression). At the equilibrium lattice constant, Tc of 715, 840, 875, and 1050 K are predicted by Monte Carlo simulation for NiMnP, NiMnAs, NiMnGe, and NiMnSi, respectively. Following these results, these alloys are strongly expected to be promising candidates for spintronic applications.抄録全体を表示PDF形式でダウンロード (406K) -
Yoshimasa Bando, Tadashi Kawamoto, Takehiko Mori, Kazuo Takimiya, Tets ...2008 年 77 巻 1 号 p. 014706
発行日: 2008/01/15
公開日: 2011/12/28
ジャーナル 認証ありUniaxial strain is applied to the incommensurate organic superconductor, (MDT-TS)(AuI2)0.441, along the three crystallographic axes, where MDT-TS is 5H-2-(1,3-diselenol-2-ylidene)-1,3,4,6-tetrathiapentalene. The metal–insulator transition temperature (TMI) exhibits almost the same uniaxial strain dependence in all directions, but the tight-binding calculation cannot explain the isotropic uniaxal strain effect. The superconducting critical pressure (Pc) decreases in the order of a>b>c. The isotropic uniaxial strain effect for TMI is quite unusual in highly anisotropic molecular conductors.抄録全体を表示PDF形式でダウンロード (563K) -
Tsuneya Ando2008 年 77 巻 1 号 p. 014707
発行日: 2008/01/15
公開日: 2011/12/28
ジャーナル 認証ありThe dependence of the frequency and broadening of optical phonons on carrier concentration is studied in carbon nanotubes within an effective-mass approximation. In metallic nanotubes, the frequency shift exhibits a logarithmic divergence and the broadening vanishes discontinuously when the Fermi level reaches the half of the optical-phonon frequency for the longitudinal mode with displacement in the axis direction, while the transverse mode is not affected. In semiconducting nanotubes, the frequency is raised for both transverse and longitudinal modes, exhibiting a behavior similar to level crossing.抄録全体を表示PDF形式でダウンロード (305K) -
Takashi Kojiri, Kazuhiko Misawa, Roy Lang2008 年 77 巻 1 号 p. 014708
発行日: 2008/01/15
公開日: 2011/12/28
ジャーナル 認証ありWe investigate dependence of photo-isomerization compositions on the time interval of a femtosecond phase-locked pulse pair used for excitation. The compositions were analyzed directly by high-performance liquid chromatograpy. Coherent enhancement of the isomerization from all-trans to 13- and 9-cis retinals was observed via the two-photon excited Ag state. We determined the dephasing time of the excited-state wave-packets to be less than 80 fs.抄録全体を表示PDF形式でダウンロード (335K) -
Toshiya Hikihara, Shoji Yamamoto2008 年 77 巻 1 号 p. 014709
発行日: 2008/01/15
公開日: 2011/12/28
ジャーナル 認証ありWe study a spin-1⁄2 two-leg Heisenberg ladder with four-spin ring exchanges under a magnetic field. We introduce an exact duality transformation, which is an extension of the spin-chirality duality developed previously and yields a new self-dual surface in the parameter space. We then determine the magnetic phase diagram using the numerical approaches of the density-matrix renormalization-group and exact diagonalization methods. We demonstrate the appearance of a magnetization plateau and a Tomonaga–Luttinger liquid with a dominant vector-chirality quasi-long-range order for a wide parameter regime of strong ring exchange. A “nematic” phase, in which magnons form bound pairs and magnon-pairing correlation functions dominate, is also identified.抄録全体を表示PDF形式でダウンロード (326K) -
Shinya Katayama, Akito Kobayashi, Yoshikazu Suzumura2008 年 77 巻 1 号 p. 014710
発行日: 2008/01/15
公開日: 2011/12/28
ジャーナル 認証ありWe investigate the formation of density waves in the zero-gap state (ZGS) which has been found in the quasi-two-dimensional organic conductor α-(BEDT-TTF)2I3 salt under the hydrostatic pressure. The ZGS exhibits the cone-like dispersion for both the conduction band and the valence band which degenerate each other at the two-dimensional wave vectors, ±k0 forming a zero gap. By using the extended Hubbard model with repulsive interaction we calculate the onset temperature of the spin density wave (SDW) as a function of the interlayer electron hopping, which by itself does not break the cone-like dispersion. It is shown that the SDW with wave number 2k0 is induced by the combined effect of the interaction, the interband excitation across the zero-gap and the interlayer hopping.抄録全体を表示PDF形式でダウンロード (417K) -
Shinji Tokudomi, Junpei Azuma, Kazutoshi Takahashi, Masao Kamada2008 年 77 巻 1 号 p. 014711
発行日: 2008/01/15
公開日: 2011/12/28
ジャーナル 認証ありThe ultrafast surface photo-voltage (SPV) effect on the p-type GaAs(100) surface has been investigated by using the time-resolved valence-band photoemission spectroscopy with the Ti:sapphire regenerative amplifier. The rise of the SPV effect has been observed on the p-type GaAs(100). The time scale of the SPV rise depends on the dopant levels, indicating the important role of the surface electric field due to the band bending. On the other hand, the rise of the SPV effect on n-type GaAs(100) is faster than the experimental time resolution of 430 fs. It is considered that the SPV rise should be caused by the transport process of the photo-excited electrons and holes in the n- and p-type GaAs(100) surfaces, respectively.抄録全体を表示PDF形式でダウンロード (185K) -
Yusuke Wakabayashi, Daisuke Bizen, Yugo Kubo, Hironori Nakao, Youichi ...2008 年 77 巻 1 号 p. 014712
発行日: 2008/01/15
公開日: 2011/12/28
ジャーナル 認証ありStructural study of orbital-ordered manganite thin films has been conducted using synchrotron radiation, and a ground state electronic phase diagram is made. The lattice parameters of four manganite thin films, Nd0.5Sr0.5MnO3 (NSMO) or Pr0.5Sr0.5MnO3 (PSMO) on (011) surfaces of SrTiO3 (STO) or [(LaAlO3)0.3(SrAl0.5Ta0.5O3)0.7] (LSAT), were measured as a function of temperature. The result shows, as expected based on previous knowledge of bulk materials, that the films’ resistivity is closely related to their structures. Observed superlattice reflections indicate that NSMO thin films have an antiferro-orbital-ordered phase as their low-temperature phase while PSMO film on LSAT has a ferro-orbital-ordered phase, and that on STO has no orbital-ordered phase. A metallic ground state was observed only in films having a narrow region of A-site ion radius, while larger ions favor ferro-orbital-ordered structure and smaller ions stabilize antiferro-orbital-ordered structure. The key to the orbital-ordering transition in (011) film is found to be the in-plane displacement along [0\\bar11] direction.抄録全体を表示PDF形式でダウンロード (431K) -
Makoto Iwata, Yoshihiro Ishibashi, Kiyoshi Deguchi2008 年 77 巻 1 号 p. 015001
発行日: 2008/01/15
公開日: 2011/12/28
ジャーナル 認証ありPDF形式でダウンロード (100K)
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