Non-Hermitian Topological Theory of Finite-Lifetime Quasiparticles: Prediction of Bulk Fermi Arc Due to Exceptional Point

TL;DR

This paper develops a topological framework for non-Hermitian quasiparticle Hamiltonians with finite lifetimes, predicting phenomena like bulk Fermi arcs and exceptional points in Dirac materials due to the interplay of band structure and quasiparticle decay.

Contribution

It introduces a novel topological theory for non-Hermitian quasiparticles, revealing new topological features such as exceptional points and Fermi arcs caused by finite quasiparticle lifetimes.

Findings

Prediction of bulk Fermi arc in Dirac materials

Identification of exceptional points in non-Hermitian quasiparticle spectra

Analysis of the effects of quasiparticle lifetime on topological properties

Abstract

We introduce a topological theory to study quasiparticles in interacting and/or disordered many-body systems, which have a finite lifetime due to inelastic and/or elastic scattering. The one-body quasiparticle Hamiltonian includes both the Bloch Hamiltonian of band theory and the self-energy due to interactions, which is non-Hermitian when quasiparticle lifetime is finite. We study the topology of non-Hermitian quasiparticle Hamiltonians in momentum space, whose energy spectrum is complex. The interplay of band structure and quasiparticle lifetime is found to have remarkable consequences in zero- and small-gap systems. In particular, we predict the existence of topological exceptional point and bulk Fermi arc in Dirac materials with two distinct quasiparticle lifetimes.