报告时间：5月15日 周三 下午2:00

报告地点：实验室一楼会议室

报告人：武汉物理与数学研究所江开军研究员

报告题目： Phase transition in a spin-orbital-angular-momentum coupled Bose-Einstein condensate

报告摘要：

Coupling between particle’s spin and orbital motion is ubiquitous in atoms, photons, solid materials and many other systems. It contributes to the topological properties like quantum-Hall effect in solid materials and electronic fine structure in atoms. Ultracold atoms with a high tunability provides an ideal platform to study spin-orbit (SO) coupling. Spin-linear-momentum (SLM) coupling has been observed in quantum gases and subsequently a variety of exotic quantum states have been explored. While the experimental study on the other kind of SO coupling, namely the spin-orbital-angular-momentum (SOAM) coupling, is still lacking.

In this talk, I will report the experimental observation of the ground-state phase diagram of the SOAM coupled Bose-Einstein condensate. By inducing a Raman transition using a pair of Gaussian and Laguerre-Gaussian (LG) laser beams, we realize SOAM coupling of ultracold atoms. We observe phase transitions when the two-photon Raman coupling strength or detuning approaches the critical value. The phase transitions are classified as the first order, which features a discontinuous jump of the angular momentum (OAM) and the spin polarization. We demonstrate the hysteresis loop across the first-order phase transition. The role of interatomic interaction on the phase transition is also elucidated.

[1] D. Zhang, T. Gao, P. Zou, L. Kong, R. Li, X. Shen, X. Chen, S. Peng, M. Zhan, H. Pu, and K. Jiang, Phys. Rev. Lett. 122, 110402 (2019)

[2] T. Gao, J. Pan, D. Zhang, L. Kong, R. Li, X. Shen, X. Chen, S. Peng, M. Zhan, W. V. Liu, and K. Jiang, arXiv: 1805.04727 (2018)

[3] T. Gao, D. Zhang, L. Kong, R. Li , K. Jiang, Chin. Phys. Lett. 35, 086701 (2018)