Topological Order and Non-Hermitian Skin Effect in Generalized Ideal Chern Bands

Jiong-Hao Wang; Christopher Ekman; Raul Perea-Causin; Hui Liu; Emil J. Bergholtz

Paper

Topological Order and Non-Hermitian Skin Effect in Generalized Ideal Chern Bands

Abstract

Fractionalization in ideal Chern bands and non-Hermitian topological physics are two active but so far separate research directions. Merging these, we generalize the notion of ideal Chern bands to the non-Hermitian realm and uncover several striking consequences both on the level of band theory and in the strongly interacting regime. Specifically, we show that the lowest band of a Kapit--Mueller lattice model with an imaginary gauge potential satisfies a generalized ideal condition with complex Berry curvature in sync with a complex quantum metric. The ideal band remains purely real and exactly flat yet all right and left eigenstates accumulate at the boundaries on a cylinder, implying a non-Hermitian skin effect without an accompanying spectral winding. The skin effect is inherited by the many-body zero modes, yielding skin-Laughlin states with an exponential profile on the lattice. Moreover, at a critical strength of non-Hermiticity there is an unconventional phase transition on the torus, which is absent on the cylinder. Our findings lead to an extension of topological order in non-Hermitian systems.