Non-Hermitian spin-orbit coupled quantum gases

The recent developments in non-Hermitian physics, open new possibilities for utilizing dissipation processes but have raised numerous open questions including the classification of topological states. In this talk, we report our experimental demonstration of non-Hermitian spin-orbit coupled quantum system with ultracold fermions. The dissipation is introduced by engineering spin-selective light scattering enabling us to engineer the energy gap and close it at the critical value of the dissipation, so-called exceptional point. We measure the energy spectrum of the system via quasimomentum-resolved Rabi spectroscopy, and identify an exceptional point where the PT symmetry transition occurs. We explore the topological feature around the exceptional point by dynamically encircling the exceptional point in the parameter space. Our work highlights the full controllability of non-Hermitian quantum system, and will set the stage for the realization of the non-Hermitian topological states and (unconventional) topological superfluid with spin-orbit coupling.