Novel transitions in S=1 spinor condensates and XY Ashkin-Teller universality
We study spin-1 polar spinor condensates with magnetic anisotropy, in two spatial dimensions at finite temperatures. The topological binding of vorticity to nematic disclinations leads to a rich phase diagram, which is captured by a U(1) version of the Ashkin-Teller model. In particular, a "cascaded" Kosterlitz-Thouless critical point, with two diverging scales, is predicted. Numerical simulations are performed to check our picture.
Podolsky, D; Berkeley, UC; Chandrasekharan, S; Vishwanath, A; Berkeley, LBL
Arxiv:0707.0695 [Cond Mat.Stat Mech]