Reduction of one-dimensional non-Hermitian point-gap topology by correlations

In spite of extensive works on the non-Hermitian topology, correlations effects remain crucial questions. We hereby analyze correlated non-Hermitian systems with special emphasis on the one-dimensional point-gap topology. Specifically, our analysis elucidates that correlations result in reduction of the topological classification $\mathbb{Z}\times \mathbb{Z} \to \mathbb{Z}$ for systems of one synthetic dimension with charge $\mathrm{U(1)}$ symmetry and spin-parity symmetry. Furthermore, we analyze an extended Hatano-Nelson chain which exhibits striking correlation effects; correlations destroy the skin effect at the non-interacting level. This fragility of the skin effect against interactions is consistent with the reduction of the point-gap topology in the one spatial dimension. The above discoveries shed new light on the topology of correlated systems and open up new directions of researches on non-Hermitian topological physics.