Non-Hermitian Squeezed Polarons

TL;DR

This paper introduces the concept of non-Hermitian squeezed polarons, revealing their unique asymmetric localization, spectrum modification, and long-time steady state appearance in ultracold atomic systems, expanding the understanding of non-Hermitian quantum phenomena.

Contribution

The work proposes a new non-Hermitian polaron phenomenon with distinctive localization and spectral properties, supported by theoretical calculations and numerical simulations.

Findings

Non-Hermitian squeezed polarons localize asymmetrically opposite to non-Hermitian pumping.

They appear in the long-time steady state, unlike Hermitian polarons.

Squeezed polarons exist in the bulk, independent of boundary conditions.

Abstract

Recent experimental breakthroughs in non-Hermitian ultracold atomic lattices have dangled tantalizing prospects in realizing exotic, hitherto unreported, many-body non-Hermitian quantum phenomena. In this work, we discover and propose an experimental platform for a radically different non-Hermitian phenomenon dubbed polaron squeezing. It is marked by a dipole-like accumulation of fermions arising from an interacting impurity in a background of non-Hermitian reciprocity-breaking hoppings. We computed their spatial density and found that, unlike Hermitian polarons which are symmetrically localized around impurities, non-Hermitian squeezed polarons localize asymmetrically in the direction opposite to conventional non-Hermitian pumping and non-perturbatively modify the entire spectrum, despite having a manifestly local profile. We investigated their time evolution and found that, saliently, they appear almost universally in the long-time steady state, unlike Hermitian polarons which only exist in the ground state. In our numerics, we also found that, unlike well-known topological or skin localized states, squeezed polarons exist in the bulk, independently of boundary conditions. Our findings could inspire the realization of many-body states in ultracold atomic setups, where a squeezed polaron can be readily detected and characterized by imaging the spatial fermionic density.