|
|
Skin effect, experimentally discovered in one dimension, describes the physical phenomenon that on an open chain, an extensive number of eigenstates of a non-Hermitian hamiltonian are localized at the end(s) of the chain. Here in two and higher dimensions, we establish a theorem that the skin effect exists, if and only if periodic-boundary spectrum of the hamiltonian covers a finite area on the complex plane. This theorem establishes the universality of the effect, because the above condition is satisfied in almost every generic non-Hermitian hamiltonian, and, unlike in one dimension, is compatible with all spatial symmetries. We propose two new types of skin effect in two and higher dimensions: the corner-skin effect where all eigenstates are localized at one corner of the system, and the geometry-dependent-skin effect where skin modes disappear for systems of a particular shape, but appear on generic polygons. An immediate corollary of our theorem is that any non-Hermitian system having exceptional points (lines) in two (three) dimensions exhibits skin effect, making this phenomenon accessible to experiments in photonic crystals, Weyl semimetals, and Kondo insulators. 报告人简介：方辰2004年于北京大学获学士学位，2011年于美国Purdue University获物理学博士学位。他先后在美国Princeton University和Massachusetts Institute of Technology任博士后。方辰于2015年11月回国，任中国科学院物理研究所副研究员，2018年8月任研究员至今。方辰的研究方向包括拓扑能带理论、非厄米能带理论，量子多体动力学等。回国之后的工作成果包括：首个提出三维高阶拓扑绝缘体的概念，确定了能带不可约表示和拓扑不变量之间的定量关系，建立了首个拓扑材料计算数据库，首次提出非厄米趋肤效应的拓扑起源等。方辰于2021年获亚太物理学会“杨振宁”奖，2021年入选科睿唯安“高引用研究者”。 |
|
