Chiral Dynamics Near Intra- and Inter-Band Exceptional Points under Dissipative Spin-Orbital-Angular-Momentum Coupling

Abstract: We study the parametric chiral dynamics of atoms under dissipative spin-orbital-angular-momentum coupling (SOAMC). With atoms confined in the ring-shaped potential of the Laguerre-Gaussian Raman beams, the SOAMC not only couples the atomic center-of-mass angular momentum to the hyperfine spins, but also mixes different bands in the radial direction. This gives rise to a series of exceptional points of two types, the intra-band and the inter-band. Leveraging the topology of the spectral Riemann surface close to these exceptional points, we demonstrate the path-dependent chiral transfer of atoms to the higher-lying bands, by evolving the system along closed loops in the parameter space. Specifically, we illustrate two distinct scenarios, characterized by different mechanisms, where the atoms can be transferred to designated SOAMC-dressed bands. Our work demonstrates the rich exceptional structure in atom gases under dissipative SOAMC, and offers a novel route toward populating higher bands.