Publications (55)
Chiral symmetry and fermion doubling in the zero-mode Landau levels of massless Dirac fermions with disorder
T. Kawarabayashi, T. Honda, H. Aoki +1
The effect of disorder on the Landau levels of massless Dirac fermions is examined for the cases with and without the fermion doubling. To tune the doubling a tight-binding model h…
The Effect of Dynamical Gauge Field on the Chiral Fermion on a boundary
H. Aoki, S. Iso, J. Nishimura +1
We study the effect of dynamical gauge field on the Kaplan's chiral fermion on a boundary in the strong gauge coupling limit in the extra dimension. To all orders of the hopping pa…
Lattice realization of the generalized chiral symmetry in two dimensions
T. Kawarabayashi, H. Aoki, Y. Hatsugai
While it has been pointed out that the chiral symmetry, which is important for the Dirac fermions in graphene, can be generalized to tilted Dirac fermions as in organic metals, suc…
Orbifold Matrix Model
H. Aoki, S. Iso, T. Suyama
We study a matrix model describing type IIB superstring in orbifold backgrounds. We particularly consider a {\bf C}^3/{\bf Z}_3 orbifold model whose six dimensional transverse spac…
Electronic structure of periodic curved surfaces -- topological band structure
H. Aoki, M. Koshino, D. Takeda +1
Electronic band structure for electrons bound on periodic minimal surfaces is differential-geometrically formulated and numerically calculated. We focus on minimal surfaces because…
IIB Matrix Model
H. Aoki, S. Iso, H. Kawai +3
We review our proposal for a constructive definition of superstring, type IIB matrix model. The IIB matrix model is a manifestly covariant model for space-time and matter which pos…
Proposal for a magnetic field induced graphene dot
P. A. Maksym, M. Roy, M. F. Craciun +3
Quantum dots induced by a strong magnetic field applied to a single layer of graphene in the perpendicular direction are investigated. The dot is defined by a model potential which…
Experiments to investigate the effects of radiative cooling on plasma jet collimation
C. D. Gregory, A. Diziere, H. Aoki +15
Preliminary experiments have been performed to investigate the effects of radiative cooling on plasma jets. Thin (3 um - 5 um) conical shells were irradiated with an intense laser,…
Three-orbital study on the orbital distillation effect in the high Tc cuprates
H. Sakakibara, K. Suzuki, H. Usui +4
Our recent study has revealed that the mixture of the dz2 orbital component into the Fermi surface suppresses Tc in the cuprates such as La2CuO4. We have also shown that applying h…
Electronic structure of periodic curved surfaces -- continuous surface versus graphitic sponge
H. Aoki, M. Koshino, D. Takeda +2
We investigate the band structure of electrons bound on periodic curved surfaces. We have formulated Schrödinger's equation with the Weierstrass representation when the surface is…
Complete Spin and Valley Polarization by Total External Reflection from Potential Barriers in Bilayer Graphene and Monolayer Transition Metal Dichalcogenides
P. A. Maksym, H. Aoki
It is shown that potential barriers in bilayer graphene (BLG) and monolayer transition metal dichalcogenides (TMDs) can split a valley unpolarized incident current into reflected a…
Duality and integer quantum Hall effect in isotropic 3D crystals
M. Koshino, H. Aoki
We show here a series of energy gaps as in Hofstadter's butterfly, which have been shown to exist by Koshino et al [Phys. Rev. Lett. 86, 1062 (2001)] for anisotropic three-dimensio…
Transitions between electron-molecule states in electrostatic quantum dots
P. A. Maksym, H. Aoki
Intermediate spin states that occur in electrostatic dots in the magnetic field regime just beyond the maximum density droplet are investigated. The 5-electron system is studied wi…
Topological analysis of the quantum Hall effect in graphene: Dirac-Fermi transition across van Hove singularities and the edge vs bulk quantum numbers
Y. Hatsugai, T. Fukui, H. Aoki
Inspired by a recent discovery of a peculiar integer quantum Hall effect (QHE) in graphene, we study QHE on a honeycomb lattice in terms of the topological quantum number, with two…
Accurate Model of a Vertical Pillar Quantum Dot
P. A. Maksym, Y. Nishi, D. G. Austing +4
An accurate model of a vertical pillar quantum dot is described. The full three dimensional structure of the device containing the dot is taken into account and this leads to an ef…
Chiral symmetry and its manifestation in optical responses in graphene: interaction and multi-layers
Y. Hatsugai, T. Morimoto, T. Kawarabayashi +2
Chiral symmetry, fundamental in the physics of graphene, guarantees the existence of topologically stable doubled Dirac cones and anomalous behaviors of the zero-energy Landau leve…
Magnetic field controlled vacuum charge in graphene quantum dots with a mass gap
P. A. Maksym, H. Aoki
The effect of a magnetic field on the charged vacuum is investigated. The field dependence of the energy levels causes jumps in the total vacuum charge that occur whenever an energ…
Electronic Structure of B-2 and States in MgB, AlB and ZrB Single Crystals
J. Nakamura, S. Nasubida, E. Kabasawa +18
The effect of electron correlation (EC) on the electronic structure in MgB, AlB and ZrB, is studied by examining the partial density of states (PDOS) of B-2 and $p…
Field-Induced SDW and Butterfly Spectrum in Three Dimensions
M. Koshino, H. Aoki, T. Osada
Landau's quantization for incompletely nested Fermi surfaces is known to give rise to magnetic-field-induced spin-density waves(FISDW) in two-dimensional organic metals. Here we sh…
Fermion Modes in Instanton-Anti-Instanton Background in (1+0)-dimensional Model
H. Aoki
We evaluate the eigenvalues of Dirac operator in the background of instanton-anti-instanton configuration (I-), in a simple (1+0)-dimensional model, and find that quas…
The Magnetic Phase Diagram and the Pressure and Field Dependence of the Fermi Surface in UGe
T. Terashima, T. Matsumoto, C. Terakura +6
The ac susceptibility and de Haas-van Alphen (dHvA) effect in UGe are measured at pressures {\it P} up to 17.7 kbar for the magnetic field {\it B} parallel to the {\it a} axis,…
Ferromagnetism in a Hubbard model for an atomic quantum wire: a realization of flat-band magnetism from even-membered rings
R. Arita, K. Kuroki, H. Aoki +6
We have examined a Hubbard model on a chain of squares, which was proposed by Yajima et al as a model of an atomic quantum wire As/Si(100), to show that the flat-band ferromagnetis…
Baryogenesis at the Electroweak Scale and Above
H. Aoki
We consider origins of the baryon asymmetry which we observe today. We review the progress of electroweak-scale baryogenesis, and show a new mechanism, string-scale baryogenesis.
Terahertz dynamics of a topologically protected state: quantum Hall effect plateaus near cyclotron resonance in a GaAs/AlGaAs heterojunction
A. V. Stier, C. T. Ellis, H. Zhang +5
We measure the Hall conductivity of a two-dimensional electron gas formed at a GaAs/AlGaAs heterojunction in the terahertz regime close to the cyclotron resonance frequency by empl…
Space-Time Structures from IIB Matrix Model
H. Aoki, S. Iso, H. Kawai +2
We derive a long distance effective action for space-time coordinates from a IIB matrix model. It provides us an effective tool to study the structures of space-time. We prove the…
Intermediate Low Spin States in a Few-electron Quantum Dot in the Regime
Y. Nishi, P. A. Maksym, D. G. Austing +4
We study the effects of electron-electron interactions in a circular few-electron vertical quantum dot in such a strong magnetic field that the filling factor . We measure…
Electronic structure of an electron on the gyroid surface, a helical labyrinth
M. Koshino, H. Aoki
Previously reported formulation for electrons on curved periodic surfaces is used to analyze the band structure of an electron bound on the gyroid surface (the only triply-periodic…
Exact continuum theory of anti-Klein tunneling in bilayer graphene
P. A. Maksym, H. Aoki
Exact conditions for anti-Klein transmission zeros are found analytically with a 4-component continuum approach which includes trigonal warping. Anti-Klein tunneling occurs at obli…
Phase Diagram for the Hofstadter butterfly and integer quantum Hall effect in three dimensions
M. Koshino, H. Aoki, T. Osada +2
We give a perspective on the Hofstadter butterfly (fractal energy spectrum in magnetic fields), which we have shown to arise specifically in three-dimensional(3D) systems in our pr…
Flat bands in Weaire-Thorpe model and silicene
Y. Hatsugai, K. Shiraishi, H. Aoki
In order to analytically capture and identify peculiarities in the electronic structure of silicene, Weaire-Thorpe(WT) model, a standard model for treating three-dimensional (3D) s…
Origin of the material dependence of in the single-layered cuprates
H. Sakakibara, H. Usui, K. Kuroki +2
In order to understand the material dependence of within the single-layered cuprates, we study a two-orbital model that considers both and orbitals. W…
Resistivity, Hall effect and Shubnikov-de Haas oscillations in CeNiSn
T. Terashima, C. Terakura, S. Uji +3
The resistivity and Hall effect in CeNiSn are measured at temperatures down to 35 mK and in magnetic fields up to 20 T with the current applied along the {\it b} axis. The resistiv…
String-Scale Baryogenesis
H. Aoki, H. Kawai
Baryogenesis scenarios at the string scale are considered. The observed baryon to entropy ratio, , can be explained in these scenarios.
Topological aspects of graphene: Dirac fermions and the bulk-edge correspondence in magnetic fields
Y. Hatsugai, T. Fukui, H. Aoki
We discuss topological aspects of electronic properties of graphene, including edge effects, with the tight-binding model on a honeycomb lattice and its extensions to show the foll…
Temperature and Angular Dependence of the Magnetoresistance in Low Dimensional Organic Metals
J. S. Qualls, J. S. Brooks, S. Uji +4
Detailed studies of the magnetoresistance of alpha-(ET)2KHg(SCN)4 and alpha-(ET)2TlHg(SCN)4 as a function of temperature, magnetic field strength, and field orientation are reporte…
Detection of pairing from the extended Aharonov-Bohm period in strongly correlated electron systems
K. Kusakabe, H. Aoki
Inspired from Sutherland's work [Phys. Rev. Lett. {\bf 74}, 816 (1995)] on detecting bound spin waves, we propose that bound electron states can be detected from the dependence of…
Anisotropy in spatial order-disorder transformations and the vortex lattice symmetry transition in and
D. Jaiswal-Nagar, T. Isshiki, N. Kimura +4
Explorations of the order-disorder transformation in vortex matter in single crystals of tetragonal structured (c/a 3) borocarbide superconductors, and $LuNi_2B_2…
Hofstadter butterfly and integer quantum Hall effect in three dimensions
M. Koshino, H. Aoki, K. Kuroki +2
For a three-dimensional lattice in magnetic fields we have shown that the hopping along the third direction, which normally tends to smear out the Landau quantization gaps, can rat…
Tomography of pairing symmetry from magnetotunneling spectroscopy -- a case study for quasi-1D organic superconductors
Y. Tanuma, K. Kuroki, Y. Tanaka +3
We propose that anisotropic -, -, or -wave pairing symmetries can be distinguished from a tunneling spectroscopy in the presence of magnetic fields, which is exemplified h…
Scaling properties of the ferromagnetic state in the Hubbard model
K. Kusakabe, H. Aoki
A numerical scaling analysis is used to show that Nagaoka's ferromagnetic state in two-dimensional Hubbard model with one hole is supersede by an antiferromagnetic (AF) state with…
Composite-Fermion Picture for the Spin-Wave Excitation in the fractional quantum Hall system
T. Nakajima, H. Aoki
Spin-wave excitation mode from the spin-polarized ground state in the fractional quantum Hall liquid with odd fractions () numerically obtained by the exact diagonaliza…
Spin-squeezed Ground States in the Bilayer Quantum Hall Ferromagnet
T. Nakajima, H. Aoki
A "squeezed-vacuum" state considered in quantum optics is shown to be realized in the ground-state wavefunction for the bilayer quantum Hall system at the total Landau level fillin…
Superconductivity in repulsive electron systems having three-dimensional disconnected Fermi surfaces
S. Onari, R. Arita, K. Kuroki +1
The idea of raising Tc in the spin-fluctuation mediated superconductivity on disconnected Fermi surfaces with the gap function changing sign across but not within the Fermi pockets…
Phase-separated Ferromagnetism in Spin-imbalanced Fermi Atoms Loaded on an Optical Ladder: a DMRG study
M. Okumura, S. Yamada, M. Machida +1
We consider repulsively-interacting cold fermionic atoms loaded on an optical ladder lattice in a trapping potential. The density-matrix renormalization-group method is used to num…
Spin-twist driven persistent current in a strongly correlated two-dimensional electron system: a manifestation of the gauge field
K. Kusakabe, H. Aoki
A persistent current, coupled with the spin state, of purely many-body origin is shown to exist in Nagaoka's ferromagnetic state in two dimensions (2D). This we regard as a manifes…
Operator Product Expansion in Two-Dimensional Quantum Gravity
H. Aoki, H. Kawai, J. Nishimura +1
We consider correlation functions of operators and the operator product expansion in two-dimensional quantum gravity. First we introduce correlation functions with geodesic distanc…
Chiral Symmetry and Electron-Electron Interaction in Many-Body Gap Formation in Graphene
Y. Hamamoto, Y. Hatsugai, H. Aoki
We study a many-body ground state of graphene in perpendicular magnetic fields. Chiral symmetry in graphene enables us to determine the many-body ground state, which turns out to b…
Composite-Fermion Analysis of the Double-Layer Fractional Quantum Hall System
T. Nakajima, H. Aoki
Effect of interlayer tunneling in the double-layer fractional quantum Hall system at the total Landau level filling of (: odd integer) is analyzed with the composite-fe…
Manifestation of spin degrees of freedom in the double fractional quantum Hall system
T. Nakajima, H. Aoki
The double fractional quantum Hall system of spin 1/2 electrons is numerically studied to predict that there exists a novel spin-unpolarized quantum liquid specific to the multi-sp…
Noncommutative Yang-Mills in IIB Matrix Model
H. Aoki, N. Ishibashi, S. Iso +3
We show that twisted reduced models can be interpreted as noncommutative Yang-Mills theory. Based upon this correspondence, we obtain noncommutative Yang-Mills theory with D-brane…
Sub-cycle multidimensional spectroscopy of strongly correlated materials
V. Valmispild, E. Gorelov, M. Eckstein +5
Strongly correlated solids are extremely complex and fascinating quantum systems, where new states continue to emerge, especially when interaction with light triggers interplay bet…
Structure and magnetism in nanocrystalline Ca(La)B films
Y. Sakuraba, H. Kato, F. Sato +3
Nanocrystalline films of La-doped CaB have been fabricated by using a rf-magnetron sputtering. Lattice expansion of up to 6% with respect to the bulk value was observed along t…
Field-angle Dependence of the Zero-Energy Density of States in the Unconventional Heavy-Fermion Superconductor CeCoIn5
H. Aoki, T. Sakakibara, H. Shishido +4
Field-angle dependent specific heat measurement has been done on the heavy-fermion superconductor CeCoIn5 down to ~ 0.29 K, in a magnetic field rotating in the tetragonal c-plane.…
Damping of the Collective Amplitude Mode in Superconductors with Strong Electron-Phonon Coupling
Y. Murakami, P. Werner, N. Tsuji +1
We study the effect of strong electron-phonon interactions on the damping of the Higgs amplitude mode in superconductors by means of non-equilibrium dynamical mean-field simulation…
4f-derived Fermi Surfaces of CeRu2(Si[1-x]Ge[x])2 near the Quantum Critical Point: Resonant Soft X-ray ARPES Study
T. Okane, T. Ohkochi, Y. Takeda +10
Angle-resolved photoelectron spectroscopy in the Ce 3d-4f excitation region was measured for the paramagnetic state of CeRu2Si2, CeRu2(Si0.82Ge0.18)2, and LaRu2Si2 to investigate t…