103 citations · 562 across the 24 of their papers we have counts for
24 papers
Gapped Dirac materials and quantum valley currents in dual-gated hBN/bilayer-graphene heterostructures
Takuya Iwasaki, Yoshifumi Morita, Kenji Watanabe +1
In gapped Dirac materials, the topological current associated with each valley can flow in opposite directions creating long-range charge-neutral valley currents. We report valley…
Dual-gated hBN/bilayer-graphene superlattices and the transitions between the insulating phases at the charge neutrality point
Takuya Iwasaki, Yoshifumi Morita, Kenji Watanabe +1
We report on transport properties in dual-gated hexagonal boron nitride (hBN)/bilayer-graphene (BLG) superlattices. Here, BLG is nontwisted, i.e., plain. This paper focuses on the…
Electron transport in folded bilayer-bilayer graphene/hexagonal boron nitride superlattices under high magnetic fields
Takuya Iwasaki, Motoi Kimata, Yoshifumi Morita +7
Employing graphene as a template, we fabricate moiré superlattices by stacking bilayer or folded bilayer-bilayer graphene (BLG or fBBLG) and hexagonal boron nitride (hBN), i.e., hB…
Single-Carrier Transport in Graphene/hBN Superlattices
Takuya Iwasaki, Shu Nakaharai, Yutaka Wakayama +4
Graphene/hexagonal boron nitride (hBN) moiré superlattices have attracted interest for use in the study of many-body effects and fractal physics in Dirac fermion systems. Many exot…
Topological Valley Currents in Bilayer Graphene/Hexagonal Boron Nitride Superlattices
Kosuke Endo, Katsuyoshi Komatsu, Takuya Iwasaki +8
Graphene superlattices have recently been attracting growing interest as an emergent class of quantum metamaterials. In this paper, we report the observation of nonlocal transport…
Fabry-Pérot resonances and a crossover to the quantum Hall regime in ballistic graphene quantum point contacts
Nurul Fariha Ahmad, Katsuyoshi Komatsu, Takuya Iwasaki +8
We report on the observation of quantum transport and interference in a graphene device that is attached with a pair of split gates to form an electrostatically-defined quantum poi…
Observation of superconductivity in bilayer graphene/hexagonal boron nitride superlattices
Satoshi Moriyama, Yoshifumi Morita, Katsuyoshi Komatsu +9
A class of low-dimensional superconductivity (SC), such as most of "atomic-layer" SCs, has survived only under certain circumstances, implying a role of the substrate. Moreover, in…
Observation of the quantum valley Hall state in ballistic graphene superlattices
K. Komatsu, Y. Morita, E. Watanabe +4
In graphene superlattices, bulk topological currents can lead to long-range charge-neutral flow and non-local resistance near Dirac points. A ballistic version of these phenomena h…
Field-induced Confined States in Graphene
S. Moriyama, Y. Morita, E. Watanabe +1
We report an approach to confine the carriers in single-layer graphene, which leads to quantum devices with field-induced quantum confinement. We demonstrated that the Coulomb-bloc…
Correlation effects on the Fermi surface of the two-dimensional Hubbard model
Y. Otsuka, Y. Morita, Y. Hatsugai
Effects of electron correlation on the Fermi surface is investigated for the two-dimensional Hubbard model by the quantum Monte Carlo method. At first, an infinitesimal doping from…
Zero-modes in the random hopping model
P. W. Brouwer, E. Racine, A. Furusaki +3
If the number of lattice sites is odd, a quantum particle hopping on a bipartite lattice with random hopping between the two sublattices only is guaranteed to have an eigenstate at…
Duality in the Azbel-Hofstadter problem and the two-dimensional d-wave superconductivity with a magnetic field
Y. Morita, Y. Hatsugai
A single-parameter family of lattice-fermion model is constructed. It is a deformation of the Azbel-Hofstadter problem by a parameter $h={$B%((BDelta}/t$ (quantum parameter). A top…
Transitions from the Quantum Hall State to the Anderson Insulator: Fa te of Delocalized States
Y. Morita, K. Ishibashi, Y. Hatsugai
Transitions between the quantum Hall state and the Anderson insulator are studied in a two dimensional tight binding model with a uniform magnetic field and a random potential. By…
Plateaux Transitions in the Pairing Model:Topology and Selection Rule
Y. Morita, Y. Hatsugai
Based on the two-dimensional lattice fermion model, we discuss transitions between different pairing states. Each phase is labeled by an integer which is a topological invariant an…
Sum Rule of the Hall Conductance in Random Quantum Phase Transition
Y. Hatsugai, K. Ishibashi, Y. Morita
The Hall conductance of two-dimensional {\it lattice} electrons with random potential is investigated. The change of due to randomness is focused on. It is a quan…
Collapse of Charge Gap in Random Mott Insulators
Y. Otsuka, Y. Morita, Y. Hatsugai
Effects of randomness on interacting fermionic systems in one dimension are investigated by quantum Monte-Carlo techniques. At first, interacting spinless fermions are studied whos…
Scaling near random criticality in two-dimensional Dirac fermions
Y. Morita, Y. Hatsugai
Recently the existence of a random critical line in two dimensional Dirac fermions is confirmed. In this paper, we focus on its scaling properties, especially in the critical regio…
Low-lying excitations around a single vortex in a d-wave superconductor
Y. Morita, M. Kohmoto, K. Maki
A full quantum-mechanical treatment of the Bogoliubov-de Gennes equation for a single vortex in a d-wave superconductor is presented. First, we find low-energy states extended in f…
Near Critical States of Random Dirac Fermions
Yoshifumi Morita, Yasuhiro Hatsugai
Random Dirac fermions in a two-dimensional space are studied numerically. We realize them on a square lattice using the -flux model with random hopping. The system preserves two…
Quasi-particle spectra around a single vortex in a d-wave superconductor
Y. Morita, M. Kohmoto, K. Maki
Using the Bogoliubov-de Gennes equation, we study quasi-particle spectra around a single vortex in a d-wave superconductor, where a magnetic field is parallel to the c-axis. In the…
Vertex Operators of the -Virasoro Algebra; Defining Relations, Adjoint Actions and Four Point Functions
H. Awata, H. Kubo, Y. Morita +2
Primary fields of the -deformed Virasoro algebra are constructed. Commutation relations among the primary fields are studied. Adjoint actions of the deformed Virasoro current on…
Superconducting correlation in the one-dimensional - model with anisotropic spin interaction and broken parity
J. Shiraishi, Y. Morita, M. Kohmoto
A variant of the one-dimensional - model with anisotropic spin interaction and broken parity is studied by the nested algebraic Bethe-ansatz method. The gapless charge excita…
Exact Results on Superconductivity due to Interband Coupling
Y. Morita, Y. Hatsugai, M. Kohmoto
We present a family of exactly solvable models at arbitrary filling in any dimensions which exhibit novel superconductivity with interband pairing. By the use of the hidden …
Universal Correlations in the random matrices and 1D particles with long range interactions in a confinement potential
Y. Morita, Y. Hatsugai, M. Kohmoto
We study the correlations between eigenvalues of the large random matrices by a renormalization group approach. The results strongly support the universality of the correlations pr…