Emergent Fermi surface in a many-body non-Hermitian Fermionic chain

TL;DR

This paper investigates how a real space Fermi surface emerges in a non-Hermitian 1D fermionic chain, revealing novel effects of non-Hermiticity on many-body quantum phenomena and their experimental realization.

Contribution

It demonstrates the emergence of a real space Fermi surface in a non-Hermitian fermionic chain and characterizes it using entanglement entropy and spectral flow analysis.

Findings

Real space Fermi surface appears in non-Hermitian fermionic chains.

Entanglement entropy reveals the interplay of thermal effects and non-Hermiticity.

Nearest neighbor repulsion induces charge density waves that affect the Fermi surface.

Abstract

Quantum degeneracy pressure (QDP) underscores the stability of matter and is arguably the most ubiquitous many-body effect. The associated Fermi surface (FS) has broad implications for physical phenomena, ranging from electromagnetic responses to entanglement entropy (EE) area law violations. Given recent fruitful studies in condensed-matter physics under effectively non-Hermitian descriptions, it becomes urgent to study how QDP and many-body interactions interplay with non-Hermitian effects. Through a prototypical critical 1D fermionic lattice with asymmetric gain/loss, a real space FS is shown to naturally emerge, in addition to any existing momentum space FS. We also carefully characterize such real space FS with the EE, via a renormalized temperature that encapsulates the interplay of thermal excitations and non-Hermiticity. Nearest neighbor repulsion is also found to induce competing charge density wave (CDW) that may erode the real space FS. The underlying physics surrounding criticality and localization is further analyzed with complex flux spectral flows. Our findings can be experimentally demonstrated with ultracold fermions in a suitably designed optical lattice.