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Sparse sampling approach to efficient ab initio and many-body calculations at finite temperature

日程 : 2021年2月19日(金) 4:00 pm - 5:00 pm 場所 : On Zoom (Please make a registration through the link below) 講師 : Assist. Prof. Hiroshi Shinaoka 所属 : 埼玉大学 世話人 : 吉見一慶 (63451)
e-mail: k-yoshimi@issp.u-tokyo.ac.jp

Efficient ab initio calculations of correlated materials at finite temperatures require compact representations of the Green’s functions both in imaginary time and in Matsubara frequency. We have recently proposed a general procedure [1] which generates sparse sampling points in time and frequency from compact orthogonal basis representations, such as Chebyshev polynomials and intermediate representation (IR) basis functions [2]. These sampling points accurately resolve the information contained in the Green’s function, and efficient transforms between different representations are formulated with minimal loss of information.
In this talk, we introduce compact orthogonal basis representations with a peculiar focus on the IR basis. As a demonstration, we apply the sparse sampling scheme to diagrammatic GW and second-order Green’s function theory calculations of a hydrogen chain of noble gas atoms and of a silicon crystal. Furthermore, we demonstrate its efficiency in Migdal-Eliashberg calculations considering the retardation effect in phonon-mediated superconductors [3]. Finally, we will briefly discuss the extensions of the sparse sampling approach to two-particle quantities [4].

[1] J. Li, M. Wallerberger, N. Chikano, C.-N. Ye, E. Gull, HS, PRB 101, 035144 (2020).
[2] HS, J. Otsuki, M. Ohzeki, K. Yoshimi, PRB 96, 035147 (2017).
[3] T. Wang, T. Nomoto, Y. Nomura, HS, J. Otsuki, T. Koretsune, R. Arita, PRB 102, 134503 (2020).
[4] M. Wallerberger*, HS*, A. Kauch, arXiv:2012.05557

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(公開日: 2021年02月01日)