Abstract
A two-dimensional spin-1 Bose gas exhibits two Berezinskii-Kosterlitz-Thouless (BKT) transitions in the easy-plane ferromagnetic phase. The higher-temperature transition is associated with superfluidity of the mass current determined predominantly by a single spin component. The lower-temperature transition is associated with superfluidity of the axial spin current, quasi-long-range order of the transverse spin density, and binding of polar-core spin vortices (PCVs). Above the spin BKT temperature, the component circulations that make up each PCV spatially separate, suggesting possible deconfinement analogous to quark deconfinement in high-energy physics. Intercomponent interactions give rise to superfluid drag between the spin components, which we calculate analytically at zero temperature. We present the mass and spin superfluid phase diagram as a function of quadratic Zeeman energy . At the system is in an isotropic spin phase with symmetry. Here the fluid response exhibits a system size dependence, suggesting the absence of a BKT transition. Despite this, for finite systems the decay of spin correlations changes from exponential to algebraic as the temperature is decreased.
- Received 29 July 2022
- Accepted 1 March 2023
DOI:https://doi.org/10.1103/PhysRevResearch.5.L012045
Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI.
Published by the American Physical Society