[Seminar] Spin-orbital-angular-momentum coupled Bose-Einstein condensate by Professor Yunbo Zhang

Abstract:

Since the first experimental realization of synthetic spin-orbit (SO) coupling induced by a pair of Raman beams in a Rb Bose-Einstein condensate (BEC), SO coupled quantum gases have emerged as one of the most active frontiers in cold-atom research. SO coupling has been realized in both bosonic and fermionic atoms. Various theoretical models based on the Raman process have been proposed and are predicted to give rise to a variety of rich many-body quantum phases. I will talk about a simple model with spin and orbit angular momentum (SOAM) coupling in a spin-1 Bose-Einstein condensate, where three internal atomic states are Raman coupled by a pair of co-propagating Laguerre-Gaussian beams. Focusing on a regime where the single-particle ground state is nearly three-fold degenerate, it is shown that the weak interatomic interaction in the condensate produces a rich phase diagram, and that a many-body Rabi oscillation between two quantum phases can be induced by a sudden quench of the quadratic Zeeman shift. Some features of the quantum phase transition and spin textures have been observed in recent two experimental groups in Wuhan and Taipei.

Biography:

Prof. Yunbo Zhang is an outstanding researcher in the fields of cold atom physics and quantum fundamental theory. A native Chinese, Prof. Zhang received his PhD in 1998 from the Institute of Physics, Chinese Academy of Sciences, under the supervision of Prof. Fu-Cho Pu and Prof. Jiu-Qing Liang and then joined the research group of Prof. Xian-Geng Zhao in the Institute of Applied Physics and Computational Mathematics in Beijing as a postdoc. He then spent 2 years in Kaiserslautern University in Germany as a Humboldt Fellow, focusing on the study of quantum tunneling effect in Bose-Einstein condensation of alkali gases in collaboration with Prof. H. J. W. Mueller-Kirsten. Later he worked as a research associate in the group of Prof. Kalle-Antti Suominen in University of Turku in Finland, where he initiated the application of homotopy theory to the classification of topological defects in spinor condensates. He became a professor of Shanxi University in 2001 and his research interests include the quantum simulation of one-dimensional exactly solvable models with cold atoms, topological excitation and spin dynamics in spinor Bose-Einstein condensation, spin-orbit coupling and topological bands in quantum gases, etc. Prof. Zhang has published more than 50 papers in Physical Review journals and his contribution in “macroscopic quantum effects in multi-component Bose-Einstein condensates” has been awarded the Second Prize of Natural Science in Shanxi Province. He has been selected to the New Century Excellent Talents of Ministry of Education and other Talents Programs in Shanxi Province. Prof. Zhang has wide collaboration with colleagues in many universities and institutes, including Tsinghua, IOP-CAS, ITP-CAS, Rice, HKU, ANU, etc.