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

Rui Wang, Onur Erten (), Baigeng Wang () and D. Y. Xing
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Rui Wang: Nanjing University
Onur Erten: Arizona State University
Baigeng Wang: Nanjing University
D. Y. Xing: Nanjing University

Nature Communications, 2019, vol. 10, issue 1, 1-9

Abstract: 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 Cc = 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.

Date: 2019
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DOI: 10.1038/s41467-018-08203-9

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