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

TL;DR

This paper introduces a microscopic model of correlated fermions in three dimensions that exhibits stable, interaction-induced fourth-order exceptional points, revealing new topological phenomena in non-Hermitian quantum many-body systems.

Contribution

It presents the first demonstration of stable, interaction-induced fourth-order exceptional points in a correlated quantum many-body system, protected by chiral symmetry.

Findings

Discovery of stable fourth-order exceptional points in a 3D correlated fermion model.

Analysis of topological and analytical properties of these exceptional points.

Demonstration of robustness against symmetry-breaking perturbations.

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 many-body 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.