Statphys Seminar (online) December 16 by Dr. Toshihiro Sato

1216 Universitt Wrzburg
Zoom

t-okubo@phys.s.u-tokyo.ac.jp

Zoom

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StatPhys Seminar @ UTokyo Hongo
sites.google.com/view/statphys-seminar

2022121614:00~15:0014(14th: 14:00-15:00, December 16, 2022)

Speaker: Dr. Toshihiro Sato (Universitt Wrzburg)

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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113-00337-3-1

19 950
e-mail: t-okubo@phys.s.u-tokyo.ac.jp
Tel: 03-5841-8890

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