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.
Highlights
Excitonic insulators are insulating states formed by the coherent condensation of electron and hole pairs into BCS-like states
We show that the formation and condensation of excitons can lead to a novel topological excitonic insulator that exhibits the parity anomaly
After careful characterization of the topological properties of the p + ip excitonic insulator, we study its possible realization on interacting topological insulator (TI) surface states
Summary
Excitonic insulators are insulating states formed by the coherent condensation of electron and hole pairs into BCS-like states. 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. Unlike the p + ip SC, it does not break the global U(1) gauge symmetry but only violates the TRS To characterize such exotic states, we propose a chiral Chern number Cc and unveil the underlying parity anomaly by deriving an effective Chern–Simons gauge theory associated with topological defects. This is further responsible for (i) fractionalized excitations with charge e/2 at vortices and (ii) a spontaneous inplane magnetization of ground state.
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
