Chern insulators are paradigmatic topological insulators known for exhibiting quantized Hall conductance even without a magnetic field. Due to their topological nature, electrons within these materials cannot be thought of as forming compact wave packets, known as Wannier functions, pivotal for defining polarization. Consequently, for decades, it has not been clear how to understand the notion of polarization in Chern insulators. In a paper published earlier this year in Physical Review Letters, Prof. Benalcazar at Emory, along with his collaborators Sachin Vaidya at MIT and Michael Rechtsman at Penn State University, resolve this long-standing issue, demonstrating that Chern insulators, and by extension, topological insulators, can indeed exhibit electric polarization, accompanied by measurable quantities. The key insight enabling these findings was the examination of an insulating interface between different crystalline domains within the bulk of a Chern insulator, which can be probed for responses to polarization free from the interference of its topological states. To corroborate their theory, the authors examine the physical implications of polarization in photonic crystal analogs of Chern insulators, making predictions that now await experimental verification.
Read Prof. Benalcazar’s article here: https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.132.116602