KEIO RESEARCHERS INFORMATION SYSTEM

Career 【 Display / hide 】

Career 【 Display / hide 】

• 2007.04

  -

  2009.08

  RIKEN, Condensed Matter Theory Laboratory, Special Postdoctoral Researcher

• 2009.09

  -

  2011.06

  University of Toronto, Department of Physics, Postdoctoral Fellow

• 2011.07

  -

  2012.08

  University of Tokyo, Department of Physics, Postdoctoral Researcher

• 2012.08

  -

  2019.03

  University of Tokyo, Department of Physics, Assistant Professor

• 2019.04

  -

  Present

  Keio University, Department of Physics, Assistant Professor

Academic Background 【 Display / hide 】

Academic Background 【 Display / hide 】

• 1999.04

  -

  2002.03

  Tokyo Institute of Technology, School of Science, Department of Physics

  University, Skipped grade(s)

• 2002.04

  -

  2004.03

  Tokyo Institute of Technology, Graduate School of Science, Department of Physics

  Graduate School, Completed, Master's course

• 2004.04

  -

  2007.03

  Tokyo Institute of Technology, Graduate School of Science, Department of Physics

  Graduate School, Completed, Doctoral course

Academic Degrees 【 Display / hide 】

Academic Degrees 【 Display / hide 】

• 博士（理学）, Tokyo Institute of Technology, Coursework, 2007.03

  Characterization of Exotic Orders in Quantum Spin Systems

Research Areas 【 Display / hide 】

Research Areas 【 Display / hide 】

• Mathematical physics/Fundamental condensed matter physics

• Atomic/Molecular/Quantum electronics

Research Keywords 【 Display / hide 】

Research Keywords 【 Display / hide 】

• topological states of matter

• ultracold atomic systems

• magnetism

Research Themes 【 Display / hide 】

Research Themes 【 Display / hide 】

• Quantum critical phenomena in non-Hermitian quantum many-body systems, 

  2015.12

  -

  Present

• Theory of frustrated magnetism of volborthite based on a coupled-trimer model, 

  2015.03

  -

  Present

• Quantum Hall physics of ultracold atomic systems in synthetic gauge fields, 

  2011.07

  -

  Present

• Elementary excitations and a spin model of multiferroic BiFeO₃, 

  2011.06

  -

  2014.09

• Orders and multiferroics in spin-1/2 frustrated ferromagnetic chains, 

  2007.05

  -

  Present

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Papers 【 Display / hide 】

Papers 【 Display / hide 】

• Symmetry-protected topological phases and competing orders in a spin- 12 XXZ ladder with a four-spin interaction

  Ogino Takuhiro, Furukawa Shunsuke, Kaneko Ryui, Morita Satoshi, Kawashima Naoki

  Physical Review B 104 （ 7 ）  2021.08

  ISSN  2469-9950

  • Access to Document (DOI)

• Intercomponent entanglement entropy and spectrum in binary Bose-Einstein condensates

  Yoshino T., Furukawa S., Ueda M.

  Physical Review A （Physical Review A)  103 （ 4 ）  2021.04

  ISSN  24699926

  　View Summary

  We study the entanglement entropy and spectrum between components in binary Bose-Einstein condensates in d spatial dimensions. We employ effective field theory to show that the entanglement spectrum exhibits an anomalous square-root dispersion relation in the presence of intercomponent tunneling (Rabi coupling) and a gapped dispersion relation in its absence. These spectral features are associated with the emergence of long-range interactions in terms of the superfluid velocity and the particle density in the entanglement Hamiltonian. Our results demonstrate that unusual long-range interactions can be emulated in a subsystem of multicomponent BECs that have only short-range interactions. We also find that for a finite Rabi coupling the entanglement entropy exhibits a volume-law scaling with subleading logarithmic corrections originating from the Nambu-Goldstone mode and the symmetry restoration for a finite volume.

  • Access to Document (DOI)

• Continuous phase transition between Néel and valence bond solid phases in a J−Q -like spin ladder system

  Ogino Takuhiro, Kaneko Ryui, Morita Satoshi, Furukawa Shunsuke, Kawashima Naoki

  Physical Review B （Physical Review B)  103 （ 8 ）  2021.02

  ISSN  2469-9950

  　View Summary

  We investigate a quantum phase transition between a Néel phase and a valence bond solid (VBS) phase, each of which breaks a different Z2 symmetry, in a spin-1/2 two-leg XXZ ladder with a four-spin interaction. The model can be viewed as a one-dimensional variant of the celebrated J-Q model on a square lattice. By means of variational uniform matrix product state calculations and an effective field theory, we determine the phase diagram of the model and present evidence that the Néel-VBS transition is continuous and belongs to the Gaussian universality class with the central charge c=1. In particular, the critical exponents β,η, and, ν are found to satisfy the constraints expected for a Gaussian transition within numerical accuracy. These exponents do not detectably change along the phase boundary while they are in general allowed to do so for the Gaussian class.

  • Access to Document (DOI)

• Magnetoelastic study on the frustrated quasi-one-dimensional spin- 12 magnet LiCuVO4

  Miyata A., Hikihara T., Furukawa S., Kremer R. K., Zherlitsyn S., Wosnitza J.

  Physical Review B （Physical Review B)  103 （ 1 ）  2021.01

  ISSN  2469-9950

  　View Summary

  We investigated the magnetoelastic properties of the quasi-one-dimensional spin-12 frustrated magnet LiCuVO4. Longitudinal-magnetostriction experiments were performed at 1.5 K in high magnetic fields of up to 60 T applied along the b axis, i.e., the spin-chain direction. The magnetostriction data qualitatively resemble the magnetization results, and saturate at Hsat≈54 T, with a relative change in sample length of ΔL/L≈1.8×10-4. Remarkably, both the magnetostriction and the magnetization evolve gradually between Hc3≈48 T and Hsat, indicating that the two quantities consistently detect the spin-nematic phase just below the saturation. Numerical analyses for a weakly coupled spin-chain model reveal that the observed magnetostriction can overall be understood within an exchange-striction mechanism. Small deviations found may indicate nontrivial changes in local correlations associated with the field-induced phase transitions.

  • Access to Document (DOI)

• Continuous Phase Transition without Gap Closing in Non-Hermitian Quantum Many-Body Systems

  Matsumoto Norifumi, Kawabata Kohei, Ashida Yuto, Furukawa Shunsuke, Ueda Masahito

  Physical Review Letters （Physical Review Letters)  125 （ 26 ）  2020.12

  ISSN  0031-9007

  　View Summary

  © 2020 American Physical Society. Contrary to the conventional wisdom in Hermitian systems, a continuous quantum phase transition between gapped phases is shown to occur without closing the energy gap Δ in non-Hermitian quantum many-body systems. Here, the relevant length scale ζ≃vLR/Δ diverges because of the breakdown of the Lieb-Robinson bound on the velocity (i.e., unboundedness of vLR) rather than vanishing of the energy gap Δ. The susceptibility to a change in the system parameter exhibits a singularity due to nonorthogonality of eigenstates. As an illustrative example, we present an exactly solvable model by generalizing Kitaev's toric-code model to a non-Hermitian regime.

  • Access to Document (DOI)

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Reviews, Commentaries, etc. 【 Display / hide 】

Reviews, Commentaries, etc. 【 Display / hide 】

• Entanglement entropy and conformal field theory

  S. Furukawa, J. Shiraishi

  BUTSURI 69   541 - 546 2014

  Introduction and explanation (scientific journal), Joint Work

  • Access to Document (DOI)

Presentations 【 Display / hide 】

Presentations 【 Display / hide 】

• Ground-state phase diagram of a spin-1/2 frustrated XXZ ladder

  T. Ogino, R. Kaneko, S. Morita, S. Furukawa

  日本物理学会2021年秋季大会 (オンライン開催) , 2021.09, Oral Presentation(general)

• Spontaneous symmetry breaking and symmetry-protected topological phases in a spin-1/2 XXZ ladder with a four-spin interaction

  T. Ogino, R. Kaneko, S. Morita, S. Furukawa, N. Kawashima

  日本物理学会第76回年次大会 (オンライン開催) , 2021.03, Oral Presentation(general)

• 人工ゲージ場中の二成分Bose-Einstein凝縮体における渦格子の集団励起と結合定数の繰り込み

  Takumi Yoshino, Shunsuke Furukawa, Masahito Ueda

  日本物理学会第76回年次大会 (オンライン開催) , 2021.03, Oral Presentation(general)

• 二成分Bose-Einstein凝縮体における成分間エンタングルメント・エントロピー

  古川俊輔, 吉野匠, 上田正仁

  日本物理学会2020年秋季大会 (オンライン開催) , 2020.09, Oral Presentation(general)

• スピンラダー系におけるNeel-VBS連続相転移の数値的検証2

  荻野卓啓, 金子隆威, 森田悟史, 川島直輝, 古川俊輔

  日本物理学会2020年秋季大会 (オンライン開催) , 2020.09, Oral Presentation(general)

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Research Projects of Competitive Funds, etc. 【 Display / hide 】

Research Projects of Competitive Funds, etc. 【 Display / hide 】

• Theoretical study of many-body effects in Bose-Einstein condensates in synthetic gauge fields

  2019.04

  -

  2020.03

  Keio Gijuku, Academic Development Funds, Shunsuke Furukawa, Research grant, Principal Investigator

• Symmetry-enriched topological phases: theoretical foundation and proposal for realization

  2018.04

  -

  2023.03

  MEXT,JSPS, Grant-in-Aid for Scientific Research, 古川　俊輔, Grant-in-Aid for Scientific Research (C), Principal Investigator

• Phase frustration in Bose-Einstein condensates in optical lattices

  2016.11

  -

  2019.03

  Matsuo Foundation, Shunsuke Furukawa, Research grant, Principal Investigator

• Exploration of topological orders in strongly correlated ultracold atomic systems and development of their fundamental theory

  2013.04

  -

  2017.03

  The University of Tokyo, FURUKAWA SHUNSUKE, Grant-in-Aid for Young Scientists (B)

  　View Summary

  Topologically ordered states exhibit a number of intriguing properties such as quantized responses and quasiparticles obeying fractional statistics. In this study, we have theoretically explored novel topologically ordered states that can be realized in highly controlled ultracold atomic systems, and investigated their physical properties. In particular, we have determined detailed ground-state phase diagrams of two-component Bose gases in synthetic gauge fields, and revealed (i) the appearance of a bosonic integer quantum Hall state with unusual edge states and (ii) a nontrivial role of time-reversal symmetry in the interaction effect. We have also shown that Bose-Einstein condensate in optical lattices can host an excitation band with nontrivial topology, and that edge states originating from it can be observed by exploiting a macroscopic quantum interference.

Awards 【 Display / hide 】

Awards 【 Display / hide 】

• The 2nd High Magnetic Field Forum Frontier Incentive Award

  Shunsuke Furukawa, 2020.12, The High Magnetic Field Forum of Japan, Theoretical studies on quantum magnets with competing ferromagnetic and antiferromagnetic interactions

  Type of Award： Awards of National Conference, Council and Symposium

  　View Description

  http://www.issp.u-tokyo.ac.jp/labs/mgsl/himag-forum/frontier.html

• The 7th Young Scientist Award of the Physical Society of Japan

  Shunsuke Furukawa, 2013.03, Physical Society of Japan, Entanglement entropy in quantum many-body systems

  Type of Award： Awards of National Conference, Council and Symposium

  　View Description

  https://www.jps.or.jp/activities/awards/jusyosya/wakate2013.html#r11
  http://www.r11.div.jps.or.jp/wakate07.html
  https://ss.scphys.kyoto-u.ac.jp/TQP/achievements/newsletters.html#no3

Courses Taught 【 Display / hide 】

Courses Taught 【 Display / hide 】

• STATISTICAL PHYSICS

  2021

• PHYSICS EXERCISE 1

  2021

• PHYSICS A

  2021

• MATHEMATICS IN PHYSICS

  2021

• LITERATURE OF PHYSICS

  2021

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