Correlation effects on non-Hermitian point-gap topology in zero dimension: Reduction of topological classification

摘要

We analyze a zero-dimensional correlated system with special emphasis on the non-Hermitian point-gap topology protected by chiral symmetry. Our analysis elucidates that correlations destroy an exceptional point on a topological transition point, which separates two topological phases in the noninteracting case; one of them is characterized by the zeroth Chern number N_(0Ch) = 0, and the other is characterized by N_(0Ch) = 2. This fact implies that correlations allow to continuously connect the two distinct topological phases in the noninteracting case without closing the point gap, which is analogous to the reduction of topological classifications by correlations in Hermitian systems. Furthermore, we also discover a Mott exceptional point, an exceptional point where only spin degrees of freedom are involved.