Does Berenzinskii-Kosterlitz-Thouless transition occur in two-dimensional spin-orbit coupled Bose gases?

 

        At low temperatures, a 3D Bose gas undergoes a second-order phase transition to form a Bose-Einstein condensate. For a 2D Bose gas, however, Mermin-Wagner-Hohenberg theorem asserts that the strong thermal fluctuations would prevent the system from forming a true long-range order. Instead, the 2D Bose gas may undergo the Berenzinskii-Kosterlitz-Thouless (BKT) transition to form a supferfluid which is characterized by a quasi long-range order.

        Recently, the synthetic spin-orbit coupling has been experimentally demonstrated in ultracold atomic gases of bosons and fermions by Raman coupling of a pair of atomic hyperfine ground states. This opens up possibilities of simulating exotic quantum matter featuring magnetic and spin–orbit effects for ultracold atoms. In this talk, we present our recent investigations, both numerical and analytical, on the dynamics of a 2D spin-orbit coupled Bose gas at finite temperatures, with a focus on how the mechanism of BKT transition is modified by the presence of SO coupling. Our preliminary results suggest that the symmetric degree of freedom (total phase) undergoes the conventional BKT transition while the asymmetric degree of freedom (relative phase) possesses a possible true long-range order.