Theory of non-Hermitian fermionic superfluidity on a honeycomb lattice: Interplay between exceptional manifolds and van Hove Singularity

TL;DR

This paper investigates non-Hermitian fermionic superfluidity on a honeycomb lattice, revealing how dissipation and the interplay of exceptional lines and van Hove singularities lead to novel phase transitions and superfluid phases.

Contribution

It introduces the concept of dissipation-induced superfluidity driven by exceptional manifolds and van Hove singularities, expanding understanding of non-Hermitian many-body physics.

Findings

Dissipation enlarges the superfluid phase with a cusp on the phase boundary.

Unconventional phase transition arises from interplay between exceptional lines and van Hove singularity.

Infinitesimal dissipation induces nontrivial superfluid solutions at critical points.

Abstract

We study the non-Hermitian fermionic superfluidity subject to dissipation of Cooper pairs on a honeycomb lattice, for which we analyze the attractive Hubbard model with a complex-valued interaction. Remarkably, we demonstrate the emergence of the dissipation-induced superfluid phase that is anomalously enlarged by a cusp on the phase boundary. We find that this unconventional phase transition originates from the interplay between exceptional lines and van Hove singularity, which has no counterpart in equilibrium. Moreover, we demonstrate that the infinitesimal dissipation induces the nontrivial superfluid solution at the critical point. Our results can be tested in ultracold atoms with photoassociation techniques by postselcting special measurement outcomes with the use of quantum-gas microscopy and can lead to understanding the NH many-body physics triggered by exceptional manifolds in open quantum systems.