Symmetry-protected exceptional rings in two-dimensional correlated systems*

Emergence of exceptional points in two-dimensional systems is one of the characteristic phenomena in non-Hermitian systems. In this talk, we elucidate the impacts of symmetry on the non-Hermitian degeneracies. In particular, we analyze correlated systems with chiral symmetry in equilibrium where the imaginary-part of the self-energy induces the non-Hermitian phenomenon. Intriguingly, our analysis discover novel topological degeneracies which we call symmetry-protected exceptional rings (SPERs). Furthermore, we demonstrate that SPERs emerge in a correlated honeycomb lattice by employing the dynamical mean-field theory combined with the numerical renormalization group.