Prediction of a topological p + ip excitonic insulator with parity anomaly.

ABSTRACT: Excitonic insulators are insulating states formed by the coherent condensation of electron and hole pairs into BCS-like states. Isotropic spatial wave functions are commonly considered for excitonic condensates since the attractive interaction among the electrons and the holes in semiconductors usually leads to s-wave excitons. Here, we propose a new type of excitonic insulator that exhibits order parameter with p?+?ip symmetry and is characterized by a chiral Chern number C_c?=?1/2. This state displays the parity anomaly, which results in two novel topological properties: fractionalized excitations with e/2 charge at defects and a spontaneous in-plane magnetization. The topological insulator surface state is a promising platform to realize the topological excitonic insulator. With the spin-momentum locking, the interband optical pumping can renormalize the surface electrons and drive the system towards the proposed p?+?ip instability.

SUBMITTER: Wang R 

PROVIDER: S-EPMC6331633 | biostudies-literature | 2019 Jan

REPOSITORIES: biostudies-literature