Phase diagram of non-Hermitian BCS superfluids in a dissipative asymmetric Hubbard model

TL;DR

This paper explores the phase diagram of non-Hermitian BCS superfluids in a dissipative Hubbard model, revealing how asymmetry and density of states influence superfluidity under loss conditions.

Contribution

It introduces a systematic analysis of non-Hermitian effects on BCS superfluidity in asymmetric Hubbard models using NH BCS theory.

Findings

Weak hopping asymmetry does not affect superfluidity.

Density of states singularity influences phase boundaries.

Results are experimentally testable with ultracold atoms.

Abstract

We investigate the non-Hermitian (NH) attractive Fermi-Hubbard model with asymmetric hopping and complex-valued interactions, which can be realized by collective one-body loss and two-body loss. By means of the NH BCS theory, we find that the weak asymmetry of the hopping does not affect the BCS superfluidity since it only affects the imaginary part of the eigenvalues of the BdG Hamiltonian. Systematic analysis in the d-dimensional hypercubic lattices clarifies that the singularity in the density of states affects the phase boundary between the normal and dissipation-induced superfluid states. Our results can be tested in ultracold atoms by using the photoassociation techniques and a nonlocal Rabi coupling with local losses and postselecting null measurement outcomes with the use of the quantum-gas microscope.