콜로키움

[2023-1 콜로키움] 2023년 05월 10일 16:30, 임준원 교수 (아주대학교 물리학과)
2023-05-22 16:35:31 조회수160

 Singular Flat Band

  • 일 시 : 2023년 05월 10일 수요일 16:30

  • 연 사 : 임 준 원 교수 (아주대학교 물리학과)

  • 장 소 : 자연과학관 B117호

  • HOST : 신 상 진 교수님

  • 초 록

A flat band is an extreme quantum localized state arising from an intriguing destructive interference of the wave function [1]. While the flat band has long been studied as an ideal platform to investigate many-body physics, it has only recently received a great deal of attention since the discovery of the flat band-induced superconductivity in twisted bilayer graphene [2]. In this colloquium, I’m going to introduce several fundamental physics of the flat band, such as (i) the unique localization nature of the flat band represented by the compact localized eigenstate and (ii) the real-space topology arising from the singularity of the Bloch wave function in momentum space accompanied by the non-contractible loop states [3,4]. The flat band with such a singularity is called the singular flat band, and the singularity is characterized by the quantum distance of the Bloch eigenstates around the singular momentum [5]. I will also talk about several interesting quantum phenomena of the singular flat band, where the quantum distance is manifested. First, the flat band exhibits anomalous Landau level structures, called the Landau level spreading, which is determined by the maximum value of the quantum distance [5]. Second, we establish a novel bulk-boundary correspondence applied to the singular flat band systems, where one can extract the bulk’s quantum distance information from the effective mass of the edge modes [6].

[1] J.-W. Rhim and B.-J. Yang, Advances in Physics: X 6 1901606 (2021).

[2] Y. Cao et al., Nature 556 43 (2018).

[3] J.-W. Rhim and B.-J. Yang, Phys. Rev. B 99 045107 (2019).

[4] J. Ma, J.-W. Rhim, et. al., Phys. Rev. Lett. 124 183901 (2020).

[5] J.-W. Rhim, K. Kim, and B.-J. Yang, Nature 584 59 (2020).

[6] C.-g. Oh, D. Cho, S. Y. Park, and J.-W. Rhim, Commun. Physics 5 320 (2022).

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