(Georgia Institute of Technology, 2023-04-30)
Chai, Xiao
Relaxation or thermalization of isolated or driven quantum systems has drawn considerable research interest, and defect formation is known to be closely related to the progress towards equilibrium or steady states. In our work, we use quasi-1D spinor Bose-Einstein condensates (BECs) as platforms to tackle such non-equilibrium problems. The spinful superfluids feature for their rich internal degrees of freedom and give rise to novel defects such as vector solitons. We report on our studies of two essential ingredients of non-equilibrium dynamics in spinor BECs, namely magnetic solitons and spin sound waves. Using a spin-dependent phase imprinting technique, we generate magnetic solitons in an antiferromagnetic spin-1 BEC, where the solitons manifest themselves as a localized spin excitation propagating upon a balanced two-component condensate. The study is then extended to three-component solitons by harnessing the underlying SO(3) symmetry of the spin-1 manifold. Moreover, we theoretically explore magnetic solitons in ferromagnetic spin-1 BECs, where the solitons behave as a local spin-flip propagating on top of a spin-polarized background. Most recently, we investigate resonance phenomena in a driven spinor BEC. By driving the quadratic Zeeman shift periodically, we observe the spin sound waves generated from the parametric amplification of the spin-mixing dynamics.