Electronic Polarization in Non-Bloch Band Theory

Hermitian topological materials are characterized by the nontrivial relation between numbers and edge modes, i.e. bulk-boundary correspondence. In non-Hermitian systems, conventional correspondence breaks down. Instead, in Su-Schrieffer-Heeger model, non-Bloch correspondence, which is winding number skin effect, proposed S. Yao Z. Wang. We introduce polarization as a quantity to detect effect. Moreover, we also discuss two-dimensional systems using with spiral boundary conditions.