吉岡 英生 (ヨシオカ ヒデオ)

Transport Properties of Zigzag Ribbons Composed of TwoDimensional Quantum Spin Hall Insulators with a Single Magnetic Impurity
2020年04月, Journal of the Physical Society of Japan, 89 (4), 043702研究論文（学術雑誌）
Phase Competition, Solitons, and Domain Walls in Neutral–Ionic Transition Systems
Phase competition and excitations in the onedimensional neutralionic transition systems are theoretically studied comprehensively. From the semiclassical treatment of the bosonized Hamiltonian, we examine the competition among the neutral (N), ferroelectricionic (Iferro), and paraelectricionic (Ipara) states. The phase transitions between them can become firstorder when the fluctuationinduced higherorder commensurability potential is considered. In particular, the description of the firstorder phase boundary between N and Iferro enables us to analyze NIferro domain walls. Soliton excitations in the three phases are described explicitly and their formation energies are evaluated across the phase boundaries. The characters of the soliton and domainwall excitations are classified in terms of the topological charge and spin. The relevance to the experimental observations in the molecular neutralionic transition systems is discussed. We ascribe the pressureinduced crossover in tetrathiafulvalenepchloranil (TTFCA) at a hightemperature region to that from the N to the Ipara state, and discuss its consequence., 2016年10月, Journal of the Physical Society of Japan, 85 (10), 104705, doi;web_of_science研究論文（学術雑誌）
TomonagaLuttinger liquid theory for metallic fullurene polymers
We investigate the low energy behavior of local density of states in metallic C60 polymers theoretically. The multichannel bosonization method is applied to electronic band structures evaluated from firstprinciples calculation, by which the effects of electronic correlation and nanoscale corrugation in the atomic configuration are fully taken into account. We obtain a closedform expression for the powerlaw anomalies in the local density of states, which successfully describes the experimental observation on the C60 polymers in a quantitative manner. An important implication from the closed form solution is the existence of an experimentally unobserved crossover at nearly a hundred millielectron volts, beyond which the powerlaw exponent of the C60 polymers should change significantly., 2016年04月, PHYSICAL REVIEW B, 93 (16), 165431, doi;web_of_science研究論文（学術雑誌）
BN上グラフェンへの局所1軸ひずみ導入法の開発
一般社団法人日本物理学会, 2015年09月, 日本物理学会講演概要集 第70巻 第2号 2015年秋季大会, 70 (2), 1019研究論文（研究会，シンポジウム資料等）
Enhancement of charge ordering by the zeeman effect in onedimensional molecular conductors
The effects of an external magnetic field on the chargeordered state are investigated within the onedimensional extended Hubbard model with a quarterfilled band. We find that the external magnetic field leads to a coexistent state with three order parameters, i.e., the charge ordering, the uniform, and the staggered magnetic moments. In addition, the amplitude of the charge ordering is shown to be enhanced by the magnetic field. © 2013 The Korean Physical Society., 2013年08月, Journal of the Korean Physical Society, 63 (3), 383  386, doi研究論文（学術雑誌）
Theoretical Studies on Phase Transitions in QuasiOneDimensional Molecular Conductors
A review is given for recent theoretical studies on phase transitions in quasionedimensional molecular conductors with a quarterfilled band. By lowering temperature, charge transfer salts exhibit a variety of transitions accompanying symmetry breaking, such as charge ordering, lattice dimerization, antiferromagnetic transition, spinPeierls distortion, and so on. Analyses on microscopic quasionedimensional models provide their systematic understandings, by the complementary use of different analytical and numerical techniques; they can reproduce finitetemperature phase transitions, whose results can be directly compared with experiments and give feedbacks to material design., 2012年09月, CRYSTALS, 2 (3), 996  1016, doi;web_of_scienceObservation of Riemannian geometric effects on electronic states
Einstein first applied Riemannian geometry to develop the general theory of relativity almost one hundred years ago and succeeded in understanding astronomicalscale phenomena such as the straining of timespace by a gravitational field. Whether or not Riemannian space affects the electronic properties of condensed matters on a much smaller scale is of great interest. Although Riemannian geometry has been applied to quantum mechanics since the 1950s, nobody has yet answered this question, because the electronic properties of materials with Riemannian geometry have not been examined experimentally. We report here the first observation of Riemannian geometrical effects on the electronic properties of materials such as TomononagaLuttinger liquids, which were previously theoretically predicted by our group. We present in situ highresolution ultraviolet photoemission spectra of a onedimensional metallic C60 polymer with an uneven periodic peanutshaped structure. Copyright (C) EPLA, 2012, 2012年04月, EPL, 98 (2), 27001, doi;web_of_science研究論文（学術雑誌）
局所歪みのあるグラフェンの電気伝導測定
一般社団法人日本物理学会, 2012年03月, 日本物理学会講演概要集, 67 (1), 885研究論文（学術雑誌）
OneDimensional Uneven PeanutShaped C60 Polymer: A Quantum Electronic System in Riemannian Space
When a C60 film is irradiated with a 3 kV electronbeam in an ultrahigh vacuum (base pressure: 10(7) Pa), C60 molecules are coalesced to form a onedimensional (1D) uneven peanutshaped C60 polymer. From a topological viewpoint, since the polymer has both positive and negative Gaussian curvatures, it can be regarded as a new allotrope of nanocarbons different from graphene, fullerenes, and nanotubes. We will present our recent results of the electronic, optical, and electrontransport properties of the 1D uneven peanutshaped C60 polymer and discuss its novel electronic properties on the basis of quantum mechanics in Riemannian space., 2012年, FULLERENES NANOTUBES AND CARBON NANOSTRUCTURES, 20 (1), 1  16, doi;web_of_science研究論文（学術雑誌）
Collapse of Charge Ordering Due to Disorder in Quasi OneDimensional Electron Systems
Effects of disorder on charge ordering ( CO) is investigated for onedimensional (1D) and quasi 1D extended Hubbard model with infinite onsite repulsion at quarter filling. Only the forward scattering due to disorder is taken into account. In the 1D model, the resistivity due to Umklapp scattering that is an origin of CO is shown to be suppressed by the forward scattering. In addition, we obtain that the CO transition temperature TCO for quasi 1D model becomes smaller with increasing strength of the forward scattering., 2012年, 26TH INTERNATIONAL CONFERENCE ON LOW TEMPERATURE PHYSICS (LT26), PTS 15, 400, 032125, doi;web_of_science研究論文（国際会議プロシーディングス）
Supercurrent through Graphene: Effects of Vanishing Density of States
The critical current through superconductorgraphenesuperconductor Josephson junction has been studied theoretically in terms of tunnel Hamiltonian approximation. In this paper we especially focus on the effects of vanishing density of state at Fermi level in monolayer graphene. We discuss a characteristic suppression of critical current at low temperature., 2012年, 26TH INTERNATIONAL CONFERENCE ON LOW TEMPERATURE PHYSICS (LT26), PTS 15, 400, 022024, doi;web_of_science研究論文（国際会議プロシーディングス）
Effects of Hopping Modulation at the Edges on Transport Properties of Zigzag Graphene Nanoribbon Attached to Two Normal Metals
Transport properties of the junction composed of graphene nanoribbon with zigzag shaped edges attached to two normal metals are theoretically investigated. In order to clarify roles of zigzag edges on the transport properties, we consider the system where the hopping at the zigzag edges are weaker than the other bond. The results are compared with the case without modulation studied previously., 2012年, 26TH INTERNATIONAL CONFERENCE ON LOW TEMPERATURE PHYSICS (LT26), PTS 15, 400, 042077, doi;web_of_science研究論文（国際会議プロシーディングス）
Incommensurate Antiferromagnetic Insulating State in (MDTTS)(AuI2)(x)
We theoretically study the metalinsulator transition in a molecular conductor (MDTTS)(AuI2)(x) composed with an incommensurate ratio (x = 0.441), where the conduction band originated from the HOMO of donor MDTTS molecules is incommensurately filled. We consider a twodimensional Hubbard model taking account of anisotropic transfer integrals in the donor layer, under a periodic potential due to the anions (AuI2)() which mismatches the donor lattice period, and investigate the ground state within meanfield approximation. An antiferromagnetic insulating state with induced charge disproportionation is obtained in the large U and delta region; the symmetry in the charge sector is unchanged from the paramagnetic metallic state realized at small U and delta, therefore this state corresponds to the incommensurate Mott insulating state predicted previously [H. Yoshioka et al.: J. Phys. Soc. Jpn. 74 (2005) 1922] based on a simplified onedimensional model., 2011年12月, JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN, 80 (12), 123702, doi;web_of_science研究論文（学術雑誌）
Electronic spectral shift of oxygenfilled (6,6) carbon nanotubes
Electronic state modulation of armchair (6,6) carbon nanotubes filled with a linear assembly of oxygen molecules is addressed theoretically. Ferromagnetic ordering of encapsulated oxygen produces a magnetic field with cylindrical symmetry, which deviates the electron's eigenenergies from those prior to the oxygen absorption. An intriguing spectral gap arises near the Fermi energy, at which the gap formation is allowed only when the tube length equals to a multiple of three in units of carbon hexagon. A possible means to detect the selective gap formation is discussed. (C) 2011 Elsevier B.V. All rights reserved., 2011年09月, CHEMICAL PHYSICS LETTERS, 513 (46), 224  228, doi;web_of_science研究論文（学術雑誌）
Density of states anomalies in multichannel quantum wires
We reformulate the TomonagaLuttinger liquid theory for quasionedimensional Fermion systems with many subbands across the Fermi energy. Our theory enables us to obtain a rigorous expression of the local density of states (LDOS) for general multichannel quantum wires, describing how the powerlaw anomalies of the LDOS depend on inter and intrasubbands couplings as well as the Fermi velocity of each band. The resulting formula for the exponents is valid in the cases of both bulk contact and edge contact, and thus plays a fundamental role in the physical properties of multicomponent TomonagaLuttinger liquid systems., 2011年08月, PHYSICAL REVIEW B, 84 (7), 075443, doi;web_of_science研究論文（学術雑誌）
Manipulating the TomonagaLuttinger exponent by electric field modulation
We establish a theoretical framework for artificial control of the powerlaw singularities in TomonagaLuttinger liquid states. The exponent governing the powerlaw behaviors is found to increase significantly with an increase in the amplitude of spatially periodic electrostatic field applied to the system. This fieldinduced shift in the exponent indicates the tunability of the transport properties of quasionedimensional electron systems., 2010年12月, EUROPEAN PHYSICAL JOURNAL B, 78 (4), 481  488, doi;web_of_science研究論文（学術雑誌）
Theoretical study of superconducting proximity effect in single and multilayered graphene
Theoretical analysis of superconducting current in graphite thin films (or graphene) in proximity to superconductors is presented, especially paying attention to the band structure. We derive the general formula to calculate the free energy of the superconductorgraphite filmsuperconductor junction, which enable us to calculate the critical current of the junction. We introduce two models for the band structures: (1) Fermi point type (characteristic to monolayer case) and (2) zerogap semiconductor type (characteristic to bilayer case). Then we calculate the superconducting critical current as a function of junction length and temperature. (C) 2009 Published by Elsevier B.V., 2010年12月, PHYSICA CSUPERCONDUCTIVITY AND ITS APPLICATIONS, 470, S846  S847, doi;web_of_science研究論文（学術雑誌）
FiniteTemperature Properties across the Charge Ordering Transition – Combined Bosonization, Renormalization Group, and Numerical Methods –
We theoretically describe the charge ordering (CO) metalinsulator transition based on a quasionedimensional extended Hubbard model, and investigate the finite temperature (T) properties across the transition temperature, TCO. In order to calculate T dependence of physical quantities such as the spin susceptibility and the electrical resistivity, both above and below TCO, a theoretical scheme is developed which combines analytical methods with numerical calculations. We take advantage of the renormalization group equations derived from the effective bosonized Hamiltonian, where Lanczos exact diagonalization data are chosen as initial parameters, while the CO order parameter at finiteT is determined by quantum Monte Carlo simulations. The results show that the spin susceptibility does not show a steep singularity at TCO, and it slightly increases compared to the case without CO because of the suppression of the spin velocity. In contrast, the resistivity exhibits a sudden increase at TCO, below which a characteristic T dependence is observed. We also compare our results with experiments on molecular conductors as well as transition metal oxides showing CO., 2010年09月, J. Phys. Soc. Jpn., 79 (9), 094714, doi;web_of_science研究論文（学術雑誌）
23pXB2 グラフェンにおける超伝導近接効果の理論II(23pXB 超伝導・電荷密度波,領域6(金属,超低温超伝導・密度波))
社団法人日本物理学会, 2010年08月, 日本物理学会講演概要集, 65 (2), 743研究論文（学術雑誌）
Anomalous Interaction Dependence in Magnetism of Graphene Nanoribbons with Zigzag Edges
The properties in magnetic ordered states of graphene nanoribbons with zigzagshaped edges are investigated by applying meanfield approximation to the Hubbard model with the onsite repulsion U. We observe that magnetic moments and critical temperature show anomalous powerlaw dependences as a function of U; the actual values of the power are determined by only the width of the ribbons. Such singular behaviours are found to be due to the localized nature of the electronic states close to the Fermi energy., 2010年08月, JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN, 79 (8), 084708, doi;web_of_science研究論文（学術雑誌）
21aGS5 数層グラフェンにおける超伝導近接効果(21aGS 領域7,領域4合同 グラフェン,領域7(分子性固体・有機導体))
社団法人日本物理学会, 2010年03月, 日本物理学会講演概要集, 65 (1), 872研究論文（学術雑誌）
Transport properties of normal metalgraphene nanoribbonnormal metal junctions
Transport properties are investigated theoretically for the junctions consisting of two normal metals and a graphene nanoribbon which has zigzag shaped edges with the electron hopping weaker than that in the other region. We find that the conductance of the present model has the same asymptotic behavior for N(L) >> 1 as that with the spatially uniform hopping in the N(L) >= 3 case, where N(L) and N are integers corresponding to length and width, respectively. The result seems to indicate that the zigzag edges do not contribute to the transport properties in the case with N(L) >> 1. (C) 2009 Elsevier B.V. All rights reserved., 2010年02月, PHYSICA ELOWDIMENSIONAL SYSTEMS & NANOSTRUCTURES, 42 (4), 722  725, doi;web_of_science研究論文（学術雑誌）
Curvature effects on collective excitations in dumbbellshaped hollow nanotubes
We investigate surfacecurvature induced alteration in the TomonagaLuttinger liquid (TLL) states of a onedimensional (1D) deformed hollow nanotube with a dumbbellshape. Periodic variation of the surface curvature along the axial direction is found to enhance the TLL exponent significantly, which is attributed to an effective potential field that acts lowenergy electrons moving on the curved surface. The present results accounts for the experimental observation of the TLL properties of 1D metallic peanutshaped fullerene polymers whose enveloping surface is assumed to be a dumbbellshaped hollow tube. (c) 2009 Elsevier B.V. All rights reserved., 2010年02月, PHYSICA ELOWDIMENSIONAL SYSTEMS & NANOSTRUCTURES, 42 (4), 1151  1154, doi;web_of_science研究論文（学術雑誌）
Superconducting proximity effect in graphene nanostructures
The superconducting proximity effect is studied theoretically for graphene(G)superconductor(S) hybrid structures. Especially SGS junction is considered and the critical current is argued focusing on its temperature and junctionlength dependences. The free energy of the total system is calculated by use of the tunneling approximation and the critical current is estimated from it. It is reported that the critical current can oscillate as a function of temperature and junctionlength in bilayer junctions. Some detailed comparison with ordinary Snormal metalS junctions is also given and both monolayer and bilayer junctions show some characteristic deviations., 2010年, INTERNATIONAL CONFERENCE ON THEORETICAL PHYSICS DUBNANANO 2010, 248, 012002, doi;web_of_science研究論文（国際会議プロシーディングス）
Theoretical Study on Transport Properties of Normal MetalZigzag Graphene NanoribbonNormal Metal Junctions
We investigate transport properties of the junctions in which the graphene nanoribbon with the zigzag shaped edges consisting of the N legs is sandwiched by the two normal metals by means of recursive Green's function method. The conductance and the transmission probabilities are found to have the remarkable properties depending on the parity of N. The singular behaviors close to E = 0 with E being the Fermi energy are demonstrated. The channel filtering is shown to occur in the case with N = even., 2009年12月, JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN, 78 (12), 123701, doi;web_of_science研究論文（学術雑誌）
26pYE9 電場下における多層グラフェンの特異な近接効果誘起超伝導転移(グラフェン電子物性(伝導特性),領域7,領域4合同,領域7,分子性固体・有機導体)
社団法人日本物理学会, 2009年08月, 日本物理学会講演概要集, 64 (2), 765研究論文（学術雑誌）
Geometrydriven shift in the TomonagaLuttinger exponent of deformed cylinders
We demonstrate the effects of geometric perturbation on the TomonagaLuttinger liquid (TLL) states in a long, thin, and hollow cylinder whose radius varies periodically. The variation in the surface curvature inherent to the system gives rise to a significant increase in the powerlaw exponent of the single particle density of states. The increase in the TLL exponent is caused by a curvatureinduced potential that attracts lowenergy electrons to region that has large curvature. © 2009 The American Physical Society., 2009年05月01日, Physical Review B  Condensed Matter and Materials Physics, 79 (20), doi研究論文（学術雑誌）
Geometrydriven shift in the TomonagaLuttinger exponent of deformed cylinders
We demonstrate the effects of geometric perturbation on the TomonagaLuttinger liquid (TLL) states in a long, thin, and hollow cylinder whose radius varies periodically. The variation in the surface curvature inherent to the system gives rise to a significant increase in the powerlaw exponent of the single particle density of states. The increase in the TLL exponent is caused by a curvatureinduced potential that attracts lowenergy electrons to region that has large curvature., 2009年05月, PHYSICAL REVIEW B, 79 (20), 201401, doi;web_of_science研究論文（学術雑誌）
Properties of nanographite ribbons with zigzag edges  Difference between odd and even legs
Persistent currents and transport properties are investigated for the nanographite ribbons with zigzag shaped edges with paying attention to system length L dependence. It is found that both the persistent current in the isolated ring and the conductance of the system connected to the perfect leads show the remarkable L dependences. In addition, the dependences for the systems with odd legs and those with even legs are different from each other. On the persistent current, the amplitude for the cases with odd legs shows powerlow behavior as L(N) with N being the number of legs, whereas the maximum of it decreases exponentially for the cases with even legs. The conductance per one spin normalized by e(2)/h behaves as follows. In the even legs cases, it decays as L(2), whereas it reaches to unity for L > infinity in the odd legs cases. Thus, the material is shown to have a remarkable property that there is the qualitative difference between the systems with odd legs and those with even legs even in the absence of the electronelectron interaction., 2009年, 25TH INTERNATIONAL CONFERENCE ON LOW TEMPERATURE PHYSICS (LT25), PART 2, 150, 022105, doi;web_of_science研究論文（国際会議プロシーディングス）
グラフェンにおける超伝導近接効果の理論(不均一超伝導超流動状態と量子物理,研究会報告)
物性研究刊行会, 2008年12月, 物性研究, 91 (3), 241研究論文（学術雑誌）
Superconducting proximity effect through graphene and graphite films
We discuss the superconducting proximity effect in graphite films (or graphene) by studying the critical current through superconductorgraphite film (or graphene)superconductor Josephson junction. The two leads are assumed to be conventional swave superconductors. We especially pay attention to the dispersions of electrons in graphite films: because of the delicate band structure of graphite, the electron dispersion in the film, which undergoes the effects of various external factors such as leads, gate electrodes and sample inhomogeneities, can show a wide variety. We introduce several models for electron dispersion near Fermi energy: 1) graphenelike Fermi points, 2) semimetal, and 3) semiconducting gap. The superconducting critical current I, through the junction is usually expressed as Ic proportional to exp{d/xi(T)}, where d is the distance between two leads and xi(T) is the proximity length. We show that the temperature dependence of (T) is largely affected by the band structure of the graphite film and by examining this dependence some insight into the electronic properties of the graphite film can be obtained., 2008年, INTERNATIONAL SYMPOSIUM ON ADVANCED NANODEVICES AND NANOTECHNOLOGY, 109, 012014, doi;web_of_science研究論文（国際会議プロシーディングス）
Mott insulating state in incommensurate molecular conductors
2008年, Journal of Physics: Conference Series, 132, 012018Chargeordered state versus DimerMott insulator at finite temperatures
We theoretically investigate the competition between chargeordered state and Mott insulating state at finite temperatures in quarterfilled quasionedimensional electron systems, by studying dimerized extended Hubbard chains with interchain Coulomb interactions. In order to take into account onedimensional fluctuations properly, we apply the bosonization method to an effective model obtained by the interchain meanfield approximation. The results show that lattice dimerization, especially in the critical region, and frustration in the interchain Coulomb interactions reduce the chargeordering phase transition temperature and enlarge the dimerMott insulating phase. We also derive a general formula of the Knight shift in the chargeordered phase and its implication to experiments is discussed., 2007年10月, JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN, 76 (10), 103701, doi;web_of_science研究論文（学術雑誌）
Knight shift in the charge ordered states of the onedimensional electron systems at 1/4 filling
Knight shift in the pure charge ordered states is calculated for the onedimensional extended Hubbard model at quarter filling. The cases of charge ordered state with a 2fold periodicity and with a 4fold one are investigated based on the meanfield theory. It is shown that splitting of the Knight shift observed below the transition temperature reflects not the periodicity enlarged by the charge ordering but the charge disproportionation. (c) 2006 Elsevier B.V. All rights reserved., 2007年03月, JOURNAL OF MAGNETISM AND MAGNETIC MATERIALS, 310 (2), E332  E334, doi;web_of_science研究論文（学術雑誌）
Finitetemperature chargeordering transition and fluctuation effects in quasi onedimensional electron systems at quarter filling
Finitetemperature chargeordering phase transition in quasi onedimensional (ID) molecular conductors is investigated theoretically, based on a quasi I D extended Hubbard model at quarter filling with interchain Coulomb repulsion Vperpendicular to. The interchain term is treated within a meanfield approximation, and the ID fluctuations in the chains are fully taken into account by the bosonization theory. Three regions are found depending on the appearance of the chargeordered state at a finite temperature when Vperpendicular to is introduced: (i) a weakcoupling region where the system transforms from a metal to a chargeordered insulator with a finite transition temperature at a finite critical value of Vperpendicular to, (ii) an intermediate region where this transition occurs by infinitesimal Vperpendicular to due to the stability of the inherent ID fluctuation, and (iii) a strongcoupling region where the charge ordered state is already realized in a purely 1D case, of which the transition temperature becomes finite with infinitesimal Vperpendicular to. An analytical formula for the Vperpendicular to dependence of the transition temperature is derived for each region., 2006年06月, JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN, 75 (6), 063706, doi;web_of_science研究論文（学術雑誌）
Theoretical aspects of charge ordering in molecular conductors
Theoretical studies on charge ordering phenomena in quarterfilled molecular (organic) conductors are reviewed. Extended Hubbard models including not only the onsite but also the intersite Coulomb repulsion are constructed in a straightforward way from the crystal structures, which serve for individual study on each material as well as for their systematic understandings. In general the intersite Coulomb interaction stabilizes Wigner crystaltype charge ordered states, where the charge localizes in an arranged manner avoiding each other, and can drive the system insulating. The variety in the lattice structures, represented by anisotropic networks in not only the electron hopping but also in the intersite Coulomb repulsion, brings about diverse problems in lowdimensional strongly correlated systems. Competitions and/or coexistences between the charge ordered state and other states are discussed, such as metal, superconductor, and the dimertype Mott insulating state which is another typical insulating state in molecular conductors. Interplay with magnetism, e.g., antiferromagnetic state and spin gapped state is considered as well. Distinct situations are pointed out: influences of the coupling to the lattice degree of freedom and effects of geometrical frustration which exists in many molecular crystals. Some related topics, such as charge order in transition metal oxides and its role in new molecular conductors, are briefly remarked., 2006年05月, JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN, 75 (5), 051009, doi;web_of_scienceKnight shift and nuclear spin relaxation rate in a chargeordered state of the onedimensional extended Hubbard model at quarter filling
We investigate Knight shift and nuclear spin relaxation rate in a chargeordered state of the onedimensional extended Hubbard model with a quarterfilled band by using RPA around the meanfield solution. It is shown that both quantities show splitting below the critical temperature of the charge order, as is experimentally observed. The relationships between the amount of the splitting in the both quantities and the charge disproportionation rate are discussed., 2006年03月, JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN, 75 (3), 034703, doi;web_of_science研究論文（学術雑誌）
Theoretical study on knight shift and nuclear spin relaxation rate in the charge ordering state of the ID quarterfilled electron system
We study theoretically the Knight shift and the nuclear spin relaxation rate in the charge ordering (CO) state of the onedimensional extended Hubbard model with a quarterfilled band. It is shown that the both quantities split into the two components below the critical temperature of CO, which is different from the halffilled case. The relationship between the amount of splitting in these quantities and the charge disproportionation rate is discussed., 2006年02月, JOURNAL OF LOW TEMPERATURE PHYSICS, 142 (34), 503  506, doi;web_of_science研究論文（学術雑誌）
Incommensurate Mott insulator in onedimensional electron systems close to quarter filling
The possibility of metalinsulator transition in molecular conductors has been studied for systems composed of donor molecules and fully ionized anions with an incommensurate ratio close to 2 : I based on the onedimensional extended Hubbard model, where donor carriers are slightly deviated from quarter filling and under an incommensurate periodic potential from anions. By the renormalization group method, the interplay between commensurability energy on the donor lattice and that from the anion potential has been studied and it has been found that an "incommensurate Mott insulator" can be generated. This theoretical finding will qualitatively explain the appearance of the insulating state in a twodimensional material with an incommensurate, 2005年07月, JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN, 74 (7), 1922  1925, doi;web_of_science研究論文（学術雑誌）
Photoemission spectroscopy on singlewall carbon nanotubes
Onedimensional nature of singlewall carbon nanotubes (SWNTs) has been investigated by the photoemission spectroscopy on SWNT samples with different diameters. We successfully observe peak structures that arise from onedimensional van Hove singularities. The spectral function and the intensity at the Fermi level both exhibit powerlaw behavior with almost identical exponents, which indicates that the metallic SWNTs are regarded as ideal onedimensional systems. (C) 2004 Elsevier B.V. All rights reserved., 2004年09月, PHYSICA BCONDENSED MATTER, 351 (34), 259  261, doi;web_of_science研究論文（学術雑誌）
Charge ordering and Knight shift in onedimensional electron systems nearly halffilling
We investigate Knight shift in the charge ordered state of the onedimensional electron system nearly halffilling. It is shown that the splitting of Knight shift occurs below the critical temperature of charge ordering. This finding is different from the case of just halffilling, where the splitting does not occur even in the charge ordered state. In addition. we find the simple relations among the difference between the shift in the charge rich site and that in the poor site and the mount of the charge transfer., 2004年04月, JOURNAL DE PHYSIQUE IV, 114, 159  161, doi;web_of_science研究論文（学術雑誌）
Electronic structure of singlewall carbon nanotubes and peapods; Photoemission study
Electronic structure of singlewall carbon nanotubes was investigated by photoemission spectroscopy. Oscillations in electronic density of states due to onedimensional van Hove singularities were clearly observed near the Fermi level, which can be well reproduced by simple tightbinding calculation with assumptions a broadening and an energy shift probably due to a charge transfer from the metal substrate. Furthermore, in the vicinity of the Fermi level, two kinds of typical powerlaw dependences were observed that can be regarded as evidence of TomonagaLuttinger liquid states. Both exponents show very similar values 0.46 and 0.48 good agreement with theoretical prediction. Results on fullerene peapod system are also discussed., 2004年, ELECTRONIC PROPERTIES OF SYNTHETIC NANOSTRUCTURES, 723, 222  226, web_of_science研究論文（国際会議プロシーディングス）
Direct observation of TomonagaLuttingerliquid state in carbon nanotubes at low temperatures
The electronic transport properties of conventional threedimensional metals are successfully described by Fermiliquid theory. But when the dimensionality of such a system is reduced to one, the Fermiliquid state becomes unstable to Coulomb interactions, and the conduction electrons should instead behave according to TomonagaLuttingerliquid (TLL) theory. Such a state reveals itself through interactiondependent anomalous exponents in the correlation functions, density of states and momentum distribution of the electrons(13). Metallic singlewalled carbon nanotubes (SWNTs) are considered to be ideal onedimensional systems for realizing TLL states(46). Indeed, the results of transport measurements on metal  SWNT and SWNT  SWNT junctions have been attributed(79) to the effects of tunnelling into or between TLLs, although there remains some ambiguity in these interpretations(10). Direct observations of the electronic states in SWNTs are therefore needed to resolve these uncertainties. Here we report angleintegrated photoemission measurements of SWNTs. Our results reveal an oscillation in the pielectron density of states owing to onedimensional van Hove singularities, confirming the onedimensional nature of the valence band. The spectral function and intensities at the Fermi level both exhibit powerlaw behaviour ( with almost identical exponents) in good agreement with theoretical predictions for the TLL state in SWNTs., 2003年12月, NATURE, 426 (6966), 540  544, doi;web_of_science研究論文（学術雑誌）
Spin excitation in nanographite ribbons with zigzag edges
Spin excitation in a nanographite ribbon with zigzag edges is investigated theoretically. Due to the strongly localized nature of the states near the Fermi energy, the effective Hamiltonian for the lowenergy physics is given by the Heisenberg Hamiltonian with the nearest neighbor exchange coupling. The action corresponding to the effective Hamiltonian is mapped to that of the O(3) nonlinear sigma model. It is shown that the spin excitation has a gap when the number of the zigzag lines is even, whereas the excitation becomes gapless in the case of an odd number of zigzag lines., 2003年09月, JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN, 72 (9), 2145  2148, doi;web_of_science研究論文（学術雑誌）
TomonagaLuttingerliquid behavior in conducting carbon nanotubes with open ends
We discuss the local density of states (LDOS) of the semiinfinite conducting carbon nanombe based on the bosonization theory of onedimensional electron systems with open boundaries. The dependences of the spatially slowly varying component of the LDOS on location, energy and temperature are investigated. (C) 2003 Elsevier Science B.V. All rights reserved., 2003年05月, PHYSICA ELOWDIMENSIONAL SYSTEMS & NANOSTRUCTURES, 18 (13), 212  213, doi;web_of_science研究論文（学術雑誌）
Excitations in the charge ordered state of onedimensional extended Hubbard model at halffilling
We investigate excitation spectra in the charge ordered state of the onedimensional extended Hubbard model at halffilling with taking account of fluctuations around the meanfield solution. The imaginary parts of the dynamical susceptibilities, the dispersion relations and the weights of the collective modes are discussed., 2003年04月, SYNTHETIC METALS, 135 (13), 551  552, doi;web_of_science研究論文（学術雑誌）
Commensurateincommensurate transition in a onedimensional dimerized electron system close to quarterfilling
We investigate electronic states upon doping (i.e., by varying the chemical potential) for a quarterfilled onedimensional electron system with a dimerization, onsite and nearestneighbor repulsive interaction. By applying the renormalization group method to the bosonized Hamiltonian, the metalinsulator transition followed by commensurateincommensurate transition is obtained for Mott insulating region as well as charge ordered insulating regime. We discuss the phase diagram on the plane of the chemical potential and the interaction. (C) 2002 Elsevier Science B.V. All rights reserved., 2003年03月, SYNTHETIC METALS, 133, 49  50, doi;web_of_science研究論文（学術雑誌）
Valenceband photoemission study of singlewall carbon nanotubes
We have performed the valenceband photoemission spectroscopy on singlewall carbon nanotubes. Characteristic peak structures originated from onedimensional van Hove singularities have been successfully observed. The peak structures are well reproduced by the calculation based on the tightbinding model taking into account a diameter distribution of nanotubes., 2003年, MOLECULAR NANOSTRUCTURES, 685, 139  142, doi;web_of_science研究論文（国際会議プロシーディングス）
TomonagaLuttingerliquid theory of metallic carbon nanotubes with open boundaries
TomonagaLuttingerliquid theory is formulated for metallic carbon nanotubes with open boundaries. Both cases of single and multiwall nanotubes are discussed. Based on this theory, spatial variation of the charge density from an edge is investigated with taking account of the shift of the chemical potential which expresses the carrier injection to the nanotube. The charge density has the spatially independent part and the oscillatory component. Roles of Coulomb interaction on the amplitude of the oscillation, the wavenumbers of it and the uniform component of the charge. density are clarified., 2002年10月, JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN, 71 (10), 2512  2519, doi;web_of_science研究論文（学術雑誌）
Magnetic fluctuations in a chargeordered state of the onedimensional extended Hubbard model with a halffilled band
Magnetic properties in a chargeordered state are examined for the extended Hubbard model at halffilling. Magnetic excitations, magnetic susceptibilities and a nuclear spin relaxation rate are calculated with taking account of fluctuations around the meanfield solution. The relevance of the present results to the observation in the 1:1 organic conductors, (TTMTTP)I3, is discussed., 2002年08月, JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN, 71 (8), 1812  1815, doi;web_of_science研究論文（学術雑誌）
NMR relaxation rate in metallic carbon nanotubes
NMR relaxation rate, T1(1), of the metallic carbon nanotube is discussed based on TomonagaLuttingerliquid theory. It is found that the Coulomb interaction leads to increase of (T1T)(1) by a power law with decreasing temperature, T. The dependence on temperature of (T1T)(1) in the multiwall nanotube (MWNT) is shown to be strongly suppressed by existence of the metallic shells in the MWNTs. (C) 2002 Elsevier Science Ltd. All rights reserved., 2002年06月, JOURNAL OF PHYSICS AND CHEMISTRY OF SOLIDS, 63 (68), 1281  1284, doi;web_of_science研究論文（学術雑誌）
Oscillator strength of metallic carbon nanotubes
Based on the tight binding method with a hopping integral between the nearestneighbor atoms, an oscillator strength integral (infinity)(0) d omega Re sigma(omega) is discussed for armchair and metallic zigzag carbon nanotubes. The formulae of the oscillator strength are derived for both types of nanotubes and are compared with the result obtained by a linear chain model. In addition, the doping dependence is investigated in the absence of the Coulomb interaction. It is shown that the oscillator strength of each carbon nanotube shows qualitatively the same doping dependence, hut the fine structure is different due to its own peculiar band structure. Some relations independent of the radius of the tube are derived; and a useful formula for determining the amount of doping is proposed., 2001年01月, JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN, 70 (1), 17  20, doi;web_of_science研究論文（学術雑誌）
Effects of nextnearestneighbor repulsion on onedimensional quarterfilled electron systems
We examine effects of the nextnearestneighbor repulsion on electronic states of a onedimensional interacting electron system which consists of quarterfilled band and interactions of onsite and nearestneighbor repulsion. We derive the effective Hamiltonian for the electrons around wave number +/k(F) (KF: Fermi wave number) and apply the renormalization group method to the bosonized Hamiltonian. It is shown that the nextnearestneighbor repulsion makes 4k(F)charge ordering unstable and suppresses the spin fluctuation. Further the excitation gaps and spin susceptibility are also evaluated., 2001年03月, JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN, 70 (3), 762  773, doi;web_of_science研究論文（学術雑誌）
Crossover from quarterfilling to halffilling in a onedimensional electron system with a dimerized and quarterfilled band
The interplay between quarterfilled and halftilled umklapp scattering has been examined by applying the renormalization group method to a onedimensional quarterfilled electron system with dimerization, onsite (U) and nearestneighbor (V) repulsive interactions. The phase diagram on the UV plane is obtained at absolute zero temperature where the Mott, insulator (the charge ordered insulator) is found for smaller (larger) V. By choosing the moderate parameter in the region of Mott insulator, it is shown that the resistivity exhibits a crossover from behavior of quarterfilling to that of halffilling with decreasing temperature., 2001年06月, JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN, 70 (6), 1460  1463, doi;web_of_science研究論文（学術雑誌）
Two kinds of metallic states in carbon nanotubes  differences in transport properties
The differences between the metallic states with two valleys (2 nu) and with one valley (1 nu), both of which are realized in carbon nanotubes, are investigated through TomonagaLuttinger liquid behaviors in the transport properties due to the impurity potential. It is shown that the effects of Coulomb interaction are stronger in the 1 nu states than in the 2 nu states. The possibility of observation of the present results in multi wall carbon nanotubes is discussed. (C) 2000 Elsevier Science Ltd. All rights reserved., 2001年01月, JOURNAL OF PHYSICS AND CHEMISTRY OF SOLIDS, 62 (12), 413  417, doi;web_of_science研究論文（学術雑誌）
Commensurability in onedimensional electron systems at quarterfilling
We examine the role of commensurability in electronic states and excitations for a onedimensional interacting electron system at quarterfilling with onsite (U), nearestneighbor (V1) and nextnearestneighbor (V2) repulsive interactions, By applying the renormalization group method to the bosonized model, it is shown that the nextnearestneighbor repulsion stabilizes 2k(F) density waves and induces the excitation gap in spin fluctuation for V2 > U/2, (C) 2000 Elsevier Science Ltd. All rights reserved., 2001年01月, JOURNAL OF PHYSICS AND CHEMISTRY OF SOLIDS, 62 (12), 419  422, doi;web_of_science研究論文（学術雑誌）
Effects of a transverse electric field on chargedensity waves
A transverse electric field (a field perpendicular to the quasionedimensional conducting chains) applied to a chargedensity wave (CDW) causes frustration in the ordered state and has similar effects to a magnetic field applied to a superconductor. We study the equilibrium states of CDW in the transverse electric field paying attention to this similarity. Corresponding to typeI and typeII superconductivity, two types of CDW are investigated. (C) 2000 Elsevier Science B.V, All rights reserved., 2000年07月, PHYSICA B, 284, 1535  1536, web_of_science研究論文（学術雑誌）
Correlation gap in onedimensional quarterfilled electron system
Umklapp scattering in an onedimensional quarterfilled electron system with both onsite U(> 0) and nearestneighbor V(> 0) interactions is examined by applying the renormalization group method to the bosonized Hamiltonian. We calculate a correlation gap, which appears for V larger than a critical value. In such a case, the spin density wave (SDW) coexists with the charge disproportion with twofold periodicity. (C) 2000 Elsevier Science B.V. All rights reserved., 2000年07月, PHYSICA B, 284, 1547  1548, web_of_science研究論文（学術雑誌）
Effects of Coulomb interaction on resistivity of metallic carbon nanotubes with impurity potential
Transport properties of two kinds of metallic states, which have been found in single wall carbon nanotubes, are examined in the presence of impurity potential and longrange Coulomb interaction. It is shown that Coulomb interaction leads to the powerlaw dependence in the resistivity as a function of temperature, and modifies the power of frequency dependence of the optical conductivity at zero temperature, which is seen in high frequency. However, the powers are different between both the states. (C) 2000 Elsevier Science B.V. All rights reserved., 2000年07月, PHYSICA B, 284, 1756  1757, web_of_science研究論文（学術雑誌）
Correlation effects in a onedimensional quarterfilled electron system with repulsive interactions
A onedimensional electron system at quarterfilling has been examined by applying the renormalization group method to a bosonized model with onsite (U) and nearestneighbor (V) repulsive interactions. By evaluating both normal scattering and Umklapp scattering perturbatively, we obtain a phase diagram in which a metallic state with a 2k(F) spin density wave (k(F) is the Fermi wave number) moles into an insulating state with charge disproportionation of a 4k(F) charge density wave with an increase in both U and V. The effect of the nextnearestneighbor repulsion is also discussed., 2000年03月, JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN, 69 (3), 651  654, doi;web_of_scienceTransport properties of disordered carbon nanotubes with longrange Coulomb interaction
Transport properties of disordered carbon nanotubes are investigated including longrange Coulomb interaction. The resistivity and optical conductivity are calculated by using the memory functional method. In addition, the effect of localization is taken into account by use of the renormalizationgroup analysis, and it is shown that the backward scattering of the intravalley and that of the intervalley cannot coexist in the localized regime. Differences between the transport properties for the metallic state with two valleys and those with one valley are discussed., 2000年03月, PHYSICAL REVIEW B, 61 (11), 7316  7319, doi;web_of_science研究論文（学術雑誌）
Correlated electrons in carbon nanotubes
Singlewall carbon nanotubes are almost ideal systems for the investigation of exotic manybody effects due to nonFermi liquid behavior of interacting electrons in one dimension. Recent theoretical and experimental results are reviewed with a focus on electron correlations. Starting from a microscopic lattice model we derive an effective phase Hamiltonian for conducting singlewall nanotubes with arbitrary chirality. The parameters of the Hamiltonian show very weak dependence on the chiral angle, which makes the lowenergy physics of conducting nanotubes universal. The temperaturedependent resistivity and frequencydependent optical conductivity of nanotubes with impurities are evaluated within the Luttingerlike model. Localization effects are studied. In particular, we found that intravalley and intervalley electron scattering can not coexist at low energies. Lowenergy properties of clean nanotubes are studied beyond the Luttinger liquid approximation. The strongest Mottlike electron instability occurs at half filling. In the Mott insulating phase electrons at different atomic sublattices form characteristic bound states. The energy gaps occur in all modes of elementary excitations and estimate at 0.01  0.1 eV. We finally discuss observability of the Mott insulating phase in transport experiments. The accent is made on the charge transfer from external electrodes which results in a deviation of the electron density from halffilling., 2000年, LOWDIMENSIONAL SYSTEMS, 544, 97  111, web_of_science研究論文（国際会議プロシーディングス）
Resistance of carbon nanotubes connected to reservoirs
A phase Hamiltonian of conducting carbon nanotubes with an arbitrary chirality is given which takes account of the long range Coulomb interaction and the microscopic lattice structure. By using this Hamiltonian, the transport properties at halffilling are investigated for the case that the system is adiabatically connected to reservoirs., 1999年06月, SYNTHETIC METALS, 103 (13), 2527  2528, doi;web_of_science研究論文（学術雑誌）
Persistent current and correlation effects in carbon nanotubes
The persistent current of interacting electrons in toroidal singlewall carbon nanotubes is evaluated within Haldane's concept: of topological excitations. The overall pattern of the persistent current corresponds to the constant interaction model, whereas the fine structure stems from the electronic exchange correlations., 1999年03月, EUROPHYSICS LETTERS, 45 (5), 598  604, doi;web_of_science研究論文（学術雑誌）
Theoretical study on the charge gap of organic conductor  Bechgaard salts
The charge gap in a quarterfilled organic conductor, which is induced hy dimerization and/or alternating potential is studied by applying the renormalization group method to the bosonized onedimensional Kamiltonian. The interplay of dimerization and alternating potential gives rise to the unconventional enhancement of the charge gap in addition to the onsite repulsive interaction. The experimental results of resistivity and optical conductivity in Bechgaard salts are examined based on the present calculation., 1999年06月, JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN, 68 (6), 1809  1812, doi;web_of_scienceUniversality of electron correlations in conducting carbon nanotubes
An effective lowenergy Hamiltonian of interacting electrons in conducting singlewall carbon nanotubes with arbitrary chirality is derived from the microscopic lattice model. The parameters of the Hamiltonian show very weak dependence on the chiral angle, which makes the lowenergy properties of conducting chiral nanotubes universal. The strongest MottLike electron instability at half filling is investigated within the selfconsistent harmonic approximation. The energy gaps occur in all modes of elementary excitations and estimate at 0.010.1 eV. [S01631829(99)506164]., 1999年04月, PHYSICAL REVIEW B, 59 (16), 10457  10460, doi;web_of_science研究論文（学術雑誌）
Electronic properties of armchair carbon nanotubes: Bosonization approach
The phase Hamiltonian of armchair carbon nanotubes at half filling and away from it is derived from the microscopic lattice model by taking the longrange Coulomb interaction into account. We investigate the lowenergy properties of the system using the renormalization group method. At half filling, the ground state is a Mott insulator with a spin gap, in which bound states of electrons are formed at different atomic sublattices., 1999年01月, PHYSICAL REVIEW LETTERS, 82 (2), 374  377, doi;web_of_science研究論文（学術雑誌）
Charge density wave in a transverse electric field
A transverse electric field (a field perpendicular to the quasionedimensional conducting chains) applied to a charge density wave (CDW) has similarities with a magnetic field applied to a superconductor: both cause frustration in the ordered state and, thus, can induce various intriguing states. We study the equilibrium states of CDW in a transverse electric field employing GinzburgLandau type effective free energy of the ordered state. We found that there are two types of CDW, corresponding to typeI and typeII superconductivity: in typeI CDW, the order is completely destroyed in the surface region as we increase the transverse field, whereas in typeII CDW the dislocations (topological defects) are created, thus avoiding the complete destruction of the order. We discuss the condition for typeI and typeII CDW., 1999年12月, JOURNAL DE PHYSIQUE IV, 9 (P10), 145  147, web_of_science研究論文（学術雑誌）
Response functions of twocoupled chains of TomonagaLuttinger liquids
Properties of fluctuations in two chains of TomonagaLuttinger liquids coupled by the interchain hopping have been studied by calculating retarded response functions chi(rho)(R)(q(x), q(y); omega) for charge and chi(sigma)(R)(q(x), q(y); omega) for spin where q(x) and q(y)(= 0 or pi) denote the longitudinal and transverse wave vector, respectively, and omega is the frequency. We have found the notable fact that the repulsive intrachain interaction results in the clear enhancement of Im chi(sigma)(R)(q(x), pi; omega) and the suppression of Im chi(rho)(R)(q(x), pi; omega) at low energies. This result indicates the importance of the dynamical effect by the spin fluctuation with q(y) = pi and small omega, which has a possibility to give rise to the attractive interaction for the electron pairing. (C) 1998 Published by Elsevier Science B.V. All rights reserved., 1998年12月, PHYSICA C, 309 (12), 151  160, doi;web_of_science研究論文（学術雑誌）
Effects of Spin Defects on SpinPeierls Systems
We study the spinPeierls states in the presence of spin defects for CuGeO3 where magnetic ions Cu2+ are replaced by nonmagnetic ones Zn2+. Based on the action for the bosonized Hamiltonian, we investigate the spatial dependence of the phase which expresses the spin fluctuation. Further, we calculate temperature dependence of the magnetic susceptibility by taking account of the spatial variation of the phase. [spinPeierls state, impurity effect, magnetic susceptibility, phase Hamiltonian, CuGeO3]. © 1998, The Japan Society of High Pressure Science and Technology. All rights reserved., 1998年, Review of High Pressure Science and Technology/Koatsuryoku No Kagaku To Gijutsu, 7, 656  658, doi研究論文（学術雑誌）
Crossover between high and low energystates in twocoupled chains of Tomonaga model
By applying the renormalization group method to twocoupled chains in the Tomonaga model, the role of interchain hopping has been studied in the entire energy region. The energy for a crossover from the perturbational regime to the relevant regime becomes smaller than that of the interchain hopping due to onedimensional fluctuations of the mutual interaction. From the calculation of response functions for charge density waves and superconducting states, the phase diagram of dominant and subdominant states has been obtained in the plane of mutual interactions with fixed energy., 1997年11月, PROGRESS OF THEORETICAL PHYSICS, 98 (5), 1045  1062, doi;web_of_science研究論文（学術雑誌）
A study of quasionedimensional conductors based on two coupled chains
Based on the bosonization method, we show that the phase transition between SDW and superconductivity of the quasionedimensional organic conductors can be understood by the crossover in the two coupled chains. Further, remarkable behaviors of the charge and spin susceptibilities with the transverse wavenumber pi are calculated as a function of the longitudinal wavenumber and the frequency., 1997年02月, SYNTHETIC METALS, 85 (13), 1613  1614, doi;web_of_science研究論文（学術雑誌）
Spin defects in spinPeierls systems
We examine spinPeierls states in the presence of spin defects for CuGeO3 where magnetic ions Cu2+ replaced by nonmagnetic ones Zn2+. Based on the action for the bosonized Hamiltonian, the state is investigated by using path integral method. The temperature of spinPeierls transition TSP and, the spin gap and the magnitude of the averaged lattice dimerization in the ground state have been calculated as a function of doping. From comparison of the present TSP with the experimental result, a good agreement is obtained for the transition temperature of Cu1deltaZndeltaGeO3 in the region of the doping rate, delta < 0.02., 1997年12月, JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN, 66 (12), 3962  3969, doi;web_of_science研究論文（学術雑誌）
Properties of fluctuations in two coupled chains of Luttinger liquids
Two chains of Luttinger liquids coupled by both interchain hopping and interchain interaction are investigated A degeneracy of two kinds of dominant states with in phase and out of phase ordering in the absence of the hopping is removed since the transverse fluctuation of charge density is completely gapful and that of spin density has two kinds of excitation with and without gap. The crucial effect of the interchain hopping on the electronic properties is studied by calculating susceptibilities., 1997年01月, JOURNAL OF LOW TEMPERATURE PHYSICS, 106 (12), 49  72, web_of_science研究論文（学術雑誌）
Topological dislocations and mixed state of charge density waves
We discuss the possibility of the ''mixed state'' in incommensurate charge density waves with threedimensional order. The mixed state is created by applying an electric field perpendicular to the chains. This state consists of topological dislocations induced by the external field and is therefore similar to the mixed states of superfluids (typeII superconductors or liquid helium II). However, the peculiar coupling of charge density waves with the electric field strongly modifies the mixed state compared to conventional superfluids. The field and temperature dependence of the properties of the mixed state are studied, and some experimental aspects are discussed., 1996年10月, PHYSICAL REVIEW LETTERS, 77 (16), 3403  3406, doi;web_of_science研究論文（学術雑誌）
Spindensity wave versus superconducting fluctuations for quasionedimensional electrons in two chains of TomonagaLuttinger liquids
We study possible states at low temperatures by applying the renormalization group method to two chains of TomonagaLuttinger liquids with both repulsive intrachain interactions and interchain hopping. As the energy decreases below the hopping energy, three distinct regions I, III, and II appear successively depending on properties of fluctuations. The crossover from the spindensity wave (SDW) state to superconducting (SC) state takes place in region UI where there are the excitation gaps of transverse charge and spin fluctuations. The competition between SDW and SC states in region III is crucial to understanding the phase diagram in the quasionedimensional organic conductors., 1996年10月, PHYSICAL REVIEW B, 54 (13), 9328  9331, doi;web_of_science研究論文（学術雑誌）
Spindensity wave versus superconducting fluctuations for quasionedimensional electrons in two chains of TomonagaLuttinger liquids
We study possible states at low temperatures by applying the renormalization group method to two chains of TomonagaLuttinger liquids with both repulsive intrachain interactions and interchain hopping. As the energy decreases below the hopping energy, three distinct regions I, III, and II appear successively depending on properties of fluctuations. The crossover from the spindensity wave (SDW) state to superconducting (SC) state takes place in region III where there are the excitation gaps of transverse charge and spin fluctuations. The competition between SDW and SC states in region III is crucial to understanding the phase diagram in the quasionedimensional organic conductors. © 1996 The American Physical Society., 1996年, Physical Review B  Condensed Matter and Materials Physics, 54 (13), 9328  9331, doi研究論文（学術雑誌）
Dielectric properties of the mixed states of charge density waves
The dielectric properties of the mixed states of charge density waves are investigated. The electric screening due to the charge density waves and the nonlinear dielectric constant are studied based on the free energy of the topological dislocations, and the observation of the mixed state in condenser geometry is discussed., 1996年, CZECHOSLOVAK JOURNAL OF PHYSICS, 46 (Suppl. S5), 2607  2608, doi;web_of_science研究論文（学術雑誌）
From two coupled chains to quasionedimensional organic conductors
Electronic states of two coupled chains of interacting electron systems are investigated by means of phase Hamiltonian, and phase transition of quasionedimensional organic conductors are discussed from the point of view of the two chains., 1996年, MOLECULAR CRYSTALS AND LIQUID CRYSTALS SCIENCE AND TECHNOLOGY SECTION AMOLECULAR CRYSTALS AND LIQUID CRYSTALS, 285, 229  234, web_of_science研究論文（学術雑誌）
ROLES OF INTERCHAIN HOPPING IN 2 COUPLED CHAINS OF TOMONAGA MODEL
Two chains of interacting spinless fermions in the presence of interchain hopping are investigated by use of phase Hamiltonian based on bosonization method. Excitation spectrum and phase diagram at absolute zero temperature are obtained by means of renormalization group method. Momentum distribution functions are also calculated. It is shown that the interchain hopping gives rise to drastic effects on properties of ground state compared to interchain interaction and is crucial to appearance of ordered states in higher dimensions., 1995年10月, JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN, 64 (10), 3811  3825, doi;web_of_science研究論文（学術雑誌）
BOSONIZATION APPROACH TO 2 CHAINS COUPLED BY THE ELECTRON HOPPING
Based on bosonization method, the system where two chains of spinless Tomonaga model are coupled by a transverse hopping is investigated. Due to the appearance of the gap in one of the two excitations, the powers of correlation functions of charge density wave and superconductivity become just the half of those in the absence of the hopping., 1995年04月, SYNTHETIC METALS, 71 (13), 1967  1968, doi;web_of_science研究論文（学術雑誌）
SPIN MAGNETISM IN MESOSCOPIC METALS
Fluctuation of spin magnetic susceptibility squareroot [deltachi(s)2] in mesoscopic metals is discussed in comparison with that of orbital magnetic susceptibility squareroot [deltachi(L)2]. It is found that a ratio squareroot [deltachi(s)2]/ squareroot [deltachi(L)2] is independent of temperature and the boundary condition and has a magnitude of the order of (1/epsilon(F)tau)2 which is much smaller than unity, epsilon(F) and tau being Fermi energy and the relaxation time of the elastic scattering, respectively. Scattering dependent on electron spin (e.g., spinorbit interaction or scattering by impurity spin in the glass state) are shown to suppress squareroot [deltachi(s)2] far more strongly than squareroot [deltachi(L)2]. The results indicate that the anomalously large fluctuation of the magnetic susceptibility compared to the average, which is expected to be observed experimentally, results from the orbital motion., 1994年02月, JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN, 63 (2), 405  408, doi;web_of_science2 COUPLED CHAINS OF TOMONAGA MODEL
Two chains of spinless Tomonaga model coupled by a transverse hopping are investigated in terms of phase Hamiltonian where separation of Fermi momentum in the presence of the hopping is taken into account explicitly. It is shown that there appears a gap in one of the two excitations by using a renormalization group method. As a result, correlation of charge density wave with interchain ordering and out of phase between the chains (superconductivity with intrachain ordering and in phase between the chains) becomes the most dominant one in the case of the repulsive (attractive) intrachain interaction., 1994年12月, JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN, 63 (12), 4298  4301, doi;web_of_scienceFLUCTUATIONS OF JOSEPHSON CURRENTS AND PERSISTENT CURRENTS IN MESOSCOPIC SPINGLASS SYSTEMS
Effects of correlation of the spin scattering between different measurements in the presence of the spin glass ordering have been investigated for mesoscopic fluctuations of Josephson currents in SNS junctions and those of persistent currents in isolated AharonovBohm (AB) rings. It is found that, because of the absence of the time reversal symmetry, fluctuations of Josephson currents do not vanish even if the phase difference of two superconductors is zero and those of persistent currents in the absence of AB flux is also not zero. Moreover the characteristic length of exponential decay of the fluctuation of Josephson currents can be much longer than that of the average., 1993年02月, JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN, 62 (2), 612  623, doi;web_of_science研究論文（学術雑誌）
PERSISTENT CURRENT OF DIRAC SEA  APPLICATION TO BISMUTH
Bismuth has been known to exhibit anomalously large diamagnetism which has been interpreted on the basis of the effective Hamiltonian of the Dirac type including spinorbit coupling. Here the persistent current in a mesoscopic ring of bismuth is calculated. It is found that the magnetic flux induces persistent currents which have a spatial spread of the order of xi = 2hupsilon/E(g) (upsilon: velocity of the 'Dirac' electron; E(G): energy gap), just as in the atomic diamagnetism whose "atomic" size is gigantic and of mesoscopic scale., 1992年10月, JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN, 61 (10), 3462  3465, doi;web_of_scienceFluctuations of Josephson Currents in Mesoscopic Systems
1992年, Transport Phenomena in Mesoscopic Systems, 263  271MESOSCOPICS AND SUPERCONDUCTIVITY
1992年, New Horizons in LowDimensional Electron Systems, 369  375THE HC/E VS HC/2E OSCILLATIONS IN THE SNS JUNCTION
The Josephson current induced by the proximity effect is studied for the SNS junction with the mesoscopic AharonovBohm ring in the normal region. The results shows that the critical current has a component with hc/e oscillation in addition to hc/2e oscillation, the former of which is particular to the mesoscopic system. The relative intensity of these two oscillation will be discussed for various cases., 1991年12月, PHYSICA C, 185, 1625  1626, doi;web_of_science研究論文（学術雑誌）
架橋構造のグラフェン・ナノリボンにおける形状による歪みのコントロール
一般社団法人日本物理学会, 2015年03月, 日本物理学会講演概要集, 70 (1), 1847研究論文（研究会，シンポジウム資料等）
Observation of Riemannian geometrical effects on electronic states
Einstein first applied Riemannian geometry to develop the general theory of relativity almost one hundred years ago and succeeded in understanding astronomicalscale phenomena such as the straining of timespace by a gravitational field. Whether or not Riemannian space affects the electronic properties of condensed matters on a much smaller scale is of great interest. Although Riemannian geometry has been applied to quantum mechanics since the 1950s, nobody has yet answered this question, because the electronic properties of materials with Riemannian geometry have not been examined experimentally. We report here the first observation of Riemannian geometrical effects on the electronic properties of materials such as TomononagaLuttinger liquids, which were previously theoretically predicted by our group. We present in situ highresolution ultraviolet photoemission spectra of a onedimensional metallic C60 polymer with an uneven periodic peanutshaped structure., 2012年, Europhysics Letters, 98 (2), 27001, doi;url研究論文（学術雑誌）
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