Recently, the Berezinskii-Kosterlitz-Thouless transition was found to be mediated by half-quantum vortices (HQVs) in two-dimensional (2D) antiferromagnetic Bose gases. We study the thermal activation of HQVs in the experimentally relevant trapped quasi-2D system and find a crossover temperature at which free HQVs proliferate at the center of the trap. Above the crossover temperature, we observe transitions corresponding to the onset of a coherent condensate and a quasicondensate and discuss the absence of a fragmented condensate. A? 2010 The American Physical Society.
Pietila, V., Simula, T., & Mottonen, M. (2010). Finite-temperature phase transitions in quasi-two-dimensional spin-1 Bose gases. Physical Review A, 81(3), 1 - 8. https://doi.org/10.1103/PhysRevA.81.033616