Title: Kosterlitz-Thouless transition and vortex-antivortex lattice melting in two-dimensional Fermi gases with $p$- or $d$-wave pairing,
Abstract: We present a theoretical study of the finite-temperature Kosterlitz-Thouless
(KT) and vortex-antivortex lattice (VAL) melting transitions in two-dimensional
Fermi gases with $p$- or $d$-wave pairing. For both pairings, when the
interaction is tuned from weak to strong attractions, we observe a quantum
phase transition from the Bardeen-Cooper-Schrieffer (BCS) superfluidity to the
Bose-Einstein condensation (BEC) of difermions. The KT and VAL transition
temperatures increase during this BCS-BEC transition and approach constant
values in the deep BEC region. The BCS-BEC transition is characterized by the
non-analyticities of the chemical potential, the superfluid order parameter,
and the sound velocities as functions of the interaction strength at both zero
and finite temperatures; however, the temperature effect tends to weaken the
non-analyticities comparing to the zero temperature case. The effect of
mismatched Fermi surfaces on the $d$-wave pairing is also studied.