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Takafumi Suzuki

  (鈴木 隆史)

Profile Information

Affiliation
准教授, 大学院 工学研究科, 兵庫県立大学
Degree
Doctor of Philosophy in Engineering(Oct, 2005, Osaka University)

Contact information
takafumi-seng.u-hyogo.ac.jp
J-GLOBAL ID
201801021278662239
researchmap Member ID
B000310103

External link

Papers

 57
  • Huan-Kuang Wu, Takafumi Suzuki, Naoki Kawashima, Wei-Lin Tu
    Physical Review Research, 6(2) 023297-023297, Jun 20, 2024  
    In this work, we study two different quantum simulators composed of molecules with dipole-dipole interaction through various theoretical and numerical tools. Our first result provides knowledge of the quantum order by disorder effect of the S=1/2 system, which is programmable in a quantum simulator composed of circular Rydberg atoms in the triangular optical lattice with a controllable diagonal anisotropy. When the numbers of up spins and down spins are equal, a set of subextensive degenerate ground states is present in the classical limit, composed of continuous strings whose configuration enjoys a large degree of freedom. Among all possible configurations, we focus on the stripe (up and down spins aligning straightly) and kinked (up and down spins forming zigzag spin chains) patterns. Adopting the the real space perturbation theory, we estimate the leading order energy correction when the nearest-neighbor spin exchange coupling, J, is considered, and the overall model becomes an effective XXZ model with a spatial anisotropy. Our calculation demonstrates a lifting of the degeneracy, favoring the stripe configuration. When J becomes larger, we adopt the infinite projected entangled-pair state (iPEPS) and numerically check the effect of degeneracy lifting. The iPEPS results show that even when the spin exchange coupling is strong the stripe pattern is still favored. Next, we study the dipolar bosonic model with tilted polar angle which can be realized through a quantum simulator composed of cold atomic gas with dipole-dipole interaction in an optical lattice. By placing the atoms in a triangular lattice and tilting the polar angle, the diagonal anisotropy can also be realized in the bosonic system. With our cluster mean-field theory calculation, we provide various phase diagrams with different tilted angles, showing the abundant underlying phases including the supersolid. Our proposal indicates realizable scenarios through quantum simulators in studying the quantum effect as well as extraordinary phases. We believe that our results indicated here can also become a good benchmark for two-dimensional quantum simulators. Published by the American Physical Society 2024
  • Matthias Gohlke, Jose Carlos Pelayo, Takafumi Suzuki
    Physical Review B, 109(22) L220410-L220410, Jun 20, 2024  Peer-reviewedCorresponding author
    The characterization of quantum spin liquid phases in Kitaev materials has been a subject of intensive studies over the recent years, both theoretically and experimentally. Most theoretical studies have focused on an isotropically interacting model with its coupling strength being equivalent on each bond in an attempt to simplify the problem. In this Letter, we study an extended spin-1/2 Kitaev-Γ model on a honeycomb lattice with an additional tuning parameter that controls the coupling strength on one of the bonds: We connect the limit of isolated Kitaev-Γ chains, which is known to exhibit an emergent SU(2)1 Tomonaga-Luttinger liquid phase [Yang , ], to the two-dimensional model. We report on an instance, in which properties of the Tomonaga-Luttinger liquid persist for finite interchain coupling forming a phase we call the proximate Tomonaga-Luttinger liquid (pTLL). This pTLL is strongly anisotropic in character analogous to , and features spinon-like excitations similar to those of the antiferromagnetic Heisenberg chain. We use numerical exact diagonalization and density matrix renormalization group on various cluster geometries in a complementary way to overcome finite-size limitations. Published by the American Physical Society 2024
  • Hyun-Yong Lee, Takafumi Suzuki, Yong Baek Kim, Naoki Kawashima
    Physical Review B, 104(2) 024417-024417, Jul 13, 2021  
    Contrasting ground states of quantum magnets with the integer- and half-integer-spin moments are the manifestation of many-body quantum interference effects. In this work, we investigate the distinct nature of the integer- and half-integer-spin quantum spin liquids in the framework of the Kitaev's model on the honeycomb lattice. The models with arbitrary spin quantum numbers are not exactly solvable in contrast to the well-known quantum spin liquid solution of the spin-1/2 system. We use the tensor-network wave functions for the integer-and half-integer-spin quantum spin liquid states to unveil the important difference between these states. We find that the distinct sign structures of the tensor-network wave function for the integer- and half-integer-spin quantum spin liquids are responsible for completely different ground states in the spatially anisotropic limit. Hence the spatial anisotropy would be a useful diagnostic test for distinguishing these quantum spin liquid states, both in the numerical computations and experiments on real materials. We support this discovery via extensive numerics including the tensor-network, DMRG, and exact diagonalization computations.
  • Takafumi Suzuki, Takuto Yamada, Sei-ichiro Suga
    Physical Review B, 103(22) 224425-224425, Jun 21, 2021  Peer-reviewed
  • Takuto Yamada, Takafumi Suzuki, Sei-ichiro Suga
    Physical Review B, 102(2) 024415-024415, Jul 13, 2020  Peer-reviewedCorresponding author

Misc.

 20
  • Youhei Yamaji, Takafumi Suzuki, Mitsuaki Kawamura
    Feb 8, 2018  
    A numerical algorithm to calculate exact finite-temperature spectra of<br /> many-body lattice Hamiltonians is formulated by combining the typicality<br /> approach and the shifted Krylov subspace method. The combined algorithm, which<br /> we name finite-temperature shifted Krylov subspace method for simulating<br /> spectra (FTK$\omega$), efficiently reproduces the canonical-ensemble<br /> probability distribution at finite temperatures with the computational cost<br /> proportional to the Fock space dimension. The present FTK$\omega$ enables us to<br /> exactly calculate finite-temperature spectra of many-body systems whose system<br /> sizes are twice larger than those handled by the canonical ensemble average and<br /> allows us to access the frequency domain without sequential real-time evolution<br /> often used in previous studies. By employing the reweighting method with the<br /> present algorithm, we obtain significant reduction of the numerical costs for<br /> temperature sweeps. Application to the Kiteav-Heisenberg model (KHM) on a<br /> honeycomb lattice demonstrates the capability of the FTK$\omega$. The KHM shows<br /> quantum phase transitions from the quantum spin liquid (QSL) phase to<br /> magnetically ordered phases when the finite Heisenberg exchange coupling is<br /> introduced. We examine temperature dependence of dynamical spin structure<br /> factors of the KHM in proximity to the QSL. It is clarified that the crossover<br /> from a spin-excitation continuum, which is a characteristic of the QSL, to a<br /> damped high-energy magnon mode occurs at temperatures higher than the energy<br /> scale of the Heisenberg couplings or the spin gap that is a signature of the<br /> QSL at zero temperature. The crossover and the closeness to the Kitaev&#039;s QSL<br /> are quantitatively measured by the width of the excitation continuum or the<br /> magnon spectrum. The present results shed new light on analysis of neutron<br /> scattering and other spectroscopy measurements on QSL candidates.
  • Takafumi Suzuki, Masahiro Sato
    May 25, 2015  
    We study the boundary nature of trapped bosonic Mott insulators in optical<br /> square lattices, by performing quantum Monte Carlo simulation. We show that a<br /> finite superfluid density generally emerges in the incommensurate-filling (IC)<br /> boundary region around the bulk Mott state, irrespectively of the width of the<br /> IC region. Both off-diagonal and density correlation functions in the IC<br /> boundary region exhibit a nearly power-law decay. The power-law behavior and<br /> superfluidity are well developed below a characteristic temperature. These<br /> results indicate that a gapless boundary mode always emerges in any atomic Mott<br /> insulators on optical lattices. This further implies that if we consider a<br /> topological insulating state in Bose or Fermi atomic systems, its boundary<br /> possesses at least two gapless modes (or coupled modes) of an above IC edge<br /> state and the intrinsic topologically-protected edge state.
  • Okubo T., Harada K., Suzuki T., Matsuo H., Lou Jie, Watanabe H., Todo S., Kawashima N.
    Meeting Abstracts of the Physical Society of Japan, 69.1.2 333, 2014  
  • Harada K., Suzuki T., Matsuo H., Okubo T., Masaki A., Watanabe H., Todo S., Kawashima N.
    Meeting Abstracts of the Physical Society of Japan, 68.1.2 404, 2013  
  • Harada K., Suzuki T., Okubo T., Matsuo H., Lou Jie, Watanabe H., Todo S., Kawashima N.
    Meeting Abstracts of the Physical Society of Japan, 68.2.2 217, 2013  

Presentations

 53

Professional Memberships

 1

Research Projects

 8