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Session for “Young” physicists

日程 : 2020年7月20日(月) 10:30 am 〜 場所 : https://sites.google.com/view/cevis2020/registration (We will send the zoom link to the registered participants) 世話人 : 押川正毅 (ex.63275)
e-mail: oshikawa@issp.u-tokyo.ac.jp

Speaker 1: Yuto Ashida (University of Tokyo, Japan)

Title: Quantum Rydberg central spin problem: remnant of integrability

Abstract: I will talk about a recently proposed variational approach to quantum impurity problems and its application to analyze dynamics of a Rydberg impurity undergoing spin-exchanging collisions in ultracold atoms [1,2]. This system realizes a new type of many-body problems combining both features of the central spin model and the Kondo problem. In particular, we predict long-lasting spin precession of the Rydberg electron spin, which is reminiscent of the (integrable) central spin problem.

[1] PRL 121, 026805; PRB 98, 024103 (2018).

[2] PRL 123, 183001; PRA 100, 043618 (2019).

Speaker 2: Moonjip Park (KAIST, Korea)

Title: Higher-Order topology in Twisted Bilayer Graphene

Abstract: There have been numerous works attempting to develop a general theory of the twisted bilayer graphene. So far, most of the previous theoretical works rely on the small-angle limit, where a simple Dirac model is approximable. However, there exist, in principle, infinitely many numbers of the large commensurate angles that do not fit in this small angle limit. In this talk, we tackle the problem of the twisted bilayer graphene at arbitrary angles. We show that all moiré patterns of twisted bilayer graphene share the same non-trivial higher-order band topology, which is irrespective of the specific angles as long as the underlying symmetries are intact. Besides, we propose a novel transport effect, which we refer to as higher-order topological instanton tunneling. We show that this tunneling effect can distinguishes the topological corner states from trivial impurity bound states.

Chair: Gil Young Cho


備考 : This event is jointly organized by the Korea Institute for Advanced Study and the University of Tokyo. “Correlated Electrons Virtual International Seminars (CEVIS)” https://sites.google.com/view/cevis2020/home
(公開日: 2020年07月13日)