Details of a Researcher - Furukawa, Shunsuke

Presentations -

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Phase diagram of a spin-1/2 XXZ ladder with four-spin ring exchange

M. Fontaine, K. Sugimoto, and S. Furukawa

[International presentation] Novel Quantum States in Condensed Matter 2022 (Kyoto University) ,

2022.10

2022.12

Poster presentation

We study the ground-state phase diagram of a spin-1/2 XXZ model with a four-spin ring exchange on a two-leg ladder. The spin-chirality duality transformation allows us to relate the regimes of weak and strong four-spin interactions. By applying the Abelian bosonization and the duality, we analyze a simplified model in which part of the four-spin interactions is removed, and predict a phase diagram that contains eight distinct gapped phases. In particular, a vector chiral ordered phase and a twisted Haldane phase appear between the scalar chiral ordered phase and the dominant vector chirality phase in the regime of strong four-spin interactions. We perform numerical simulations for both the simplified and full models to confirm the predicted phase structure.

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

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

[Domestic presentation] 日本物理学会2022年秋季大会 (オンライン開催) ,

2022.09

Oral presentation (general)

Magnetic properties of volborthite determined by a coupled-trimer model

S. Furukawa and T. Momoi

[International presentation] International Workshop on Microscopic Properties of Quantum Materials (Hokkaido University) ,

2022.08

Oral presentation (invited, special)

ボース気体およびスピン梯子におけるトポロジカル相：対称性による保護と富化

古川俊輔

物性基礎工学研究グループセミナー,

2022.07

Public lecture, seminar, tutorial, course, or other speech

Theory of volborthite based on a coupled trimer model

Shunsuke Furukawa

[Domestic presentation] 17th Quantum Spin Workshop (沖縄県那覇市ともかぜ振興会館およびオンライン) ,

2022.04

Oral presentation (general)

強磁性・反強磁性相互作用の競合する量子磁性体の理論的研究

古川俊輔

[Domestic presentation] 強磁場コラボラトリーセミナー（強磁場フォーラムフロンティア奨励賞受賞講演） (東京大学物性研究所) ,

2022.03

Public lecture, seminar, tutorial, course, or other speech

Quantum entanglement in topological phases and symmetry-broken phases

古川俊輔

[International presentation] Quantum Information Entropy in Physics (京都大学基礎物理学研究所) ,

2022.03

Oral presentation (invited, special)

I will review some applications of entanglement entropy (EE) and entanglement spectra (ES) in quantum many-body systems. In a variety of topological phases, it has been found that the ES has a similar structure as the edge-mode spectrum. The "cut and glue" picture gives a physical explanation of this remarkable entanglement-edge correspondence [1]. I will explain a simple formulation of this picture based on two coupled (chiral) Tomonaga-Luttinger liquids [2]. The obtained ES can be used to derive the so-called topological entropy. In systems with continuous symmetry breaking, the EE shows a subleading logarithmic term whose coefficient is related to the number of Nambu-Goldstone modes [3]. Furthermore, the ES shows a "tower of states" structure reminiscent of the finite-size energy spectrum. I will explain the emergence of analogous features in the intercomponent entanglement in binary Bose-Einstein condensates [4].

[1] X.-L. Qi, H. Katsura, and A.W.W. Ludwig, Phys. Rev. Lett. 108, 196402 (2012).
[2] R. Lundgren, Y. Fuji, S. Furukawa, and M. Oshikawa, Phys. Rev. B 88, 245137 (2013).
[3] M. A. Metlitski and T. Grover, arXiv:1112.5166.
[4] T. Yoshino, S. Furukawa, and M. Ueda, Phys. Rev. A 103, 043321 (2021).

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

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

[Domestic presentation] 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

[Domestic presentation] 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

[Domestic presentation] 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

[Domestic presentation] 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

[Domestic presentation] 日本物理学会2020年秋季大会 (オンライン開催) ,

2020.09

Oral presentation (general)

ボルボサイトにおけるDzyaloshinskii-Moriya相互作用の効果II

古川俊輔, 桃井勉

[Domestic presentation] 日本物理学会第75回年次大会 (名古屋大学東山キャンパス) ,

2020.03

Poster presentation

多成分ボース気体の量子ホール物理：対称性による保護と富化

古川俊輔

[Domestic presentation] Bose-Einstein凝縮体の数学的側面 (近畿大学東大阪キャンパス) ,

2020.02

Oral presentation (invited, special)

対称性が課されたもとで現れる多彩なトポロジカル相に注目が集まっている。対称性のもとで初めてトポロジカルな性質を獲得する相を「対称性で保護されたトポロジカル相」、もともと持っていたトポロジカルな性質が多様化されて現れる相を「対称性で多様化（富化）されたトポロジカル相」と呼ぶ。冷却原子系の持つ高い操作性を利用して、これらの相を実現できるかどうかは興味深い。冷却原子系においては、構成原子の多様さに加え、近年、磁場やスピン・軌道結合と同等の効果を光学的に誘起する人工ゲージ場の技術も発展している。ここでは、人工磁場中のn成分ボース気体の示す量子ホール状態についての我々の最近の研究を紹介し、対称性による保護と富化について議論する。

Quantum fluctuations of vortex lattices in binary Bose-Einstein condensates: Phase diagrams and intercomponent entanglement

T. Yoshino, S. Furukawa, M. Ueda

[International presentation] International Conference on Topological Materials Science 2019 (TopoMat2019) (Kyoto University) ,

2019.12

Poster presentation

Quantum fluctuations of vortex lattices in binary Bose-Einstein condensates: Phase diagrams and intercomponent entanglement

T. Yoshino, S. Furukawa, M. Ueda

[International presentation] The 4th Kyoto-Beijing-Tokyo Workshop on Ultracold Atomic Gases (Yukawa Institute for Theoretical Physics, Kyoto University) ,

2019.09

Poster presentation

Fractional quantum Hall states with symmetry-enriched edge modes in multicomponent Bose gases

S. Furukawa, M. Ueda

[International presentation] Frontiers of Statistical Physics (FSP2019) (Hongo Campus, Univ. of Tokyo) ,

2019.06

Poster presentation

Dzyaloshinskii-Moriya interactions in volborthite: magnetic orders and thermal Hall effect

S. Furukawa, T. Momoi

[International presentation] Topological Phases and Functionality of Correlated Electron Systems (TPFC 2019) (ISSP, Univ. of Tokyo) ,

2019.02

Poster presentation