MURI Seminar 05/03/2022: Quantized polarization and fractional corner charge in Chern insulators

Sachin Vaidya from Penn State University will present a talk titled “Quantized polarization and fractional corner charge in Chern insulators”. 

Abstract:

Electronic states in Chern insulators are characterized by a topological invariant, the Chern number, that presents an obstruction to the construction of exponentially localized Wannier functions; the states therefore do not admit a Wannier representation. Here, we ask the question: Are polarization and corner charge, two concepts that rely on the states having a Wannier representation, well defined in Chern insulators? We show that these quantities can be meaningful at the boundary between two Chern insulators with the same Chern number and are quantized in the presence of inversion symmetry. We present our results using a tight-binding model as well as a realistic gyro-magnetic photonic crystal. Through this exercise and generalizations to 3D, we thus demonstrate the application of the bulk-boundary correspondence principle in novel scenarios.