title: Effects of spin-orbit coupling on the Berezinskii-Kosterlitz-Thouless transition and the vortex-antivortex structure in two-dimensional Fermi gases.
abstract: We investigate the Berezinskii-Kosterlitz-Thouless (BKT) transition in a 2D Fermi gas with spin-orbit coupling (SOC), as a function of the two-body binding energy and a perpendicular Zeeman field. By including a generic form of the SOC, as a function of Rashba and Dresselhaus terms, we study the evolution between the experimentally relevant equal Rashba-Dresselhaus (ERD) case and the Rashba-only (RO) case. We show that in the ERD case, at a fixed nonzero Zeeman field, the BKT transition temperature T(BKT) is increased by the presence of SOC for all values of the binding energy. We also find a significant increase in the value of the Clogston limit compared to the case without SOC. Furthermore, we demonstrate that the superfluid density tensor becomes anisotropic (except in the RO case), leading to an anisotropic phase-fluctuation action that describes elliptic vortices and antivortices, which become circular in the RO limit. This deformation constitutes an important experimental signature for superfluidity in a 2D Fermi gas with ERD SOC. Finally, we show that the anisotropic sound velocities exhibit anomalies at low temperatures, in the vicinity of quantum phase transitions between topologically distinct uniform superfluid phases.
authors.affiliation: School of Physics, Georgia Institute of Technology, Atlanta 30332, USA and TQC, Universiteit Antwerpen, B-2610 Antwerpen, Belgium.
authors.forename: Jeroen P A
authors.initials: JP
authors.lastname: Devreese
authors.affiliation: TQC, Universiteit Antwerpen, B-2610 Antwerpen, Belgium and Lyman Laboratory of Physics, Harvard University, Cambridge, Massachusetts 02138, USA.
authors.forename: Jacques
authors.initials: J
authors.lastname: Tempere
authors.affiliation: School of Physics, Georgia Institute of Technology, Atlanta 30332, USA.
authors.forename: Carlos A R
authors.initials: CA
authors.lastname: Sá de Melo