計算物性物理メーリングリストのみなさま
東大の大久保です。
先ほど送ったメールが文字化けしていたようです。
申し訳ありませんでした。
原因と思われる箇所を修正して、再送信しています。
12月16日に Universitat Wurzburg の佐藤年裕さんによるセミナーを以下の内容で
オンライン（Zoom）で開催します。
参加をご希望の方は大久保
t-okubo@phys.s.u-tokyo.ac.jp
までご連絡ください。
折り返し、Zoomの接続情報を送ります。
よろしくお願いいたします。
大久保 毅
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統計力学セミナー StatPhys Seminar @ UTokyo Hongo
sites.google.com/view/statphys-seminar
2022年12月16日（金）14:00~15:00（第14回）(14th: 14:00-15:00, December 16, 2022)
Speaker: Dr. Toshihiro Sato (Universitat Wurzburg)
Title: A fermionic quantum Monte Carlo approach to frustrated spin systems
Abstract:
Monte Carlo methods are exact: for a given lattice size and temperature, we obtain the correct result. However, many spin and fermion models suffer from the infamous negative sign problem that renders the computational cost exponential in the volume of the system and in the inverse temperature. A key question is hence how to optimize the sign problem in the absence of sign-free formulations. In this talk, we introduce a phase pinning approach in the realm of the auxiliary field quantum Monte Carlo algorithm to mitigate the severity of the sign problem inherent to Monte Carlo methods of frustrated spin models [1]. This allows us to access high-temperature properties of the aforementioned models and, for instance, carry out exact quantum Monte Carlo simulations in a window of temperatures relevant to experiments for various frustrated magnets. As an example, we study a generalized Kitaev model on a honeycomb lattice. The generalized Kitaev model describes a frustrated spin system which
, among other spin orders, supports a spin liquid phase [2]. It is also of remarkable interest due to its relation to honeycomb compounds such as the family of layered iridates and a ruthenium chloride. In fact we show that this phase pinning approach has the ability of reproducing experimental data of the material ruthenium chloride for the so-called magnetotropic coefficient that measures the magnetic rigidity [3]. Using this phase pinning approach, we also introduce a negative sign free formulation of the auxiliary field quantum Monte Carlo algorithm for a set of generalized Kitaev models with higher symmetries [4].
[1] T. Sato and F. F. Assaad, Phys. Rev. B. 104, L081106 (2021).
[2] A. Kitaev, Annals of Physics 321, 2 (2006).
[3] K. A. Modic, et al. Nature Physics (2020).
[4] T. Sato and F. F. Assaad, Phys. Rev. B. 106, 155110 (2022).
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大久保 毅
東京大学大学院理学系研究科 量子ソフトウェア寄付講座
特任准教授
〒113-0033 東京都文京区本郷7-3-1
東京大学大学院理学系研究科知の物理学研究センター
理学部1号館9階 950
e-mail: t-okubo@phys.s.u-tokyo.ac.jp
Tel: 03-5841-8890
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