Kinked linear response from non-Hermitian pumping

Abstract

Non-Hermiticity is known to give rise to modified topological bulk-boundary correspondences, which predict the presence of topological boundary modes through appropriately modified topological invariants. Yet, little is currently known about how non-Hermiticity affects the precise linear response of wavepackets beyond their overall spectral flow. In this work, we discover that generically, non-Hermiticity gives rise to abrupt and prominent kinks in the semi-classical wavepacket trajectories of quantum gases, despite the absence of sudden physical impulses. This physically stems from a hitherto under-appreciated intrinsic non-locality from non-Hermitian pumping, even if all physical couplings are local, thereby resulting in enigmatic singularities in the band structure that lead to discontinuous band geometry and Berry curvature. For concrete experimental demonstration, we propose an ultracold atomic setup in a two-dimensional optical lattice with laser-induced loss, such that response kinks can be observed without fine-tuning in the physical atomic cloud dynamics. Our results showcases unique non-monotonic behavior from non-Hermitian pumping beyond the non-Hermitian skin effect, and suggests new avenues for investigating non-Hermitian dynamics in ultracold atomic platforms.Comment: 21 pages, 7 figure