Fourth-Order Exceptional Points in Correlated Quantum Many-Body Systems

Abstract

Non-Hermtian (NH) Hamiltonians effectively describing the physics of dissipative systems have become an important tool with applications ranging from classical meta-materials to quantum manybody systems. Exceptional points, the NH counterpart of spectral degeneracies, are among the paramount phenomena unique to the NH realm. While realizations of second-order exceptional points have been reported in a variety of microscopic models, higher-order ones have largely remained elusive in the many-body context, as they in general require fine tuning in high-dimensional parameter spaces. Here, we propose a microscopic model of correlated fermions in three spatial dimensions and demonstrate the occurrence of interaction-induced fourth-order exceptional points that are protected by chiral symmetry. We demonstrate their stability against symmetry breaking perturbations and investigate their characteristic analytical and topological properties.

Reservoir-assisted symmetry breaking and coalesced zero-energy modes in an open PT-symmetric Su-Schrieffer-Heeger model

“…In either case, we note the occurrence of higher-order exceptional points at the intersection of lower-order exceptional manifolds 72 . We also comment that while some recent studies have investigated the properties of EP4s in certain physical contexts [73][74][75] , it is relatively rare to come across them unintentionally. Hence, it could be interesting to investigate if there is a more general correspondence between these kind of gap closings and higher-order exceptional points in open PT -symmetric systems.…”

Classification of Exceptional Nodal Topologies Protected by $\mathcal{PT}$ Symmetry

“…Note added: Shortly after our initial posting of this manuscript an independent work showing how symmetry protected 4EPs may naturally be realized in three-dimensional correlated many-body systems occured [43].…”