Quasiparticle specific heat of two-component Fermi mixtures: The atomic 163Dy-40K mixture

Abstract

Ultracold Fermi gases can enter a regime of normal superfluid phase separation, with an unpolarized superfluid component surrounded by a partially polarized normal component. Mass-imbalanced two-component Fermi mixtures on the Bardeen Cooper Schrieffer side of the crossover are studied using mean-field theory within the local density approximation, assuming s-wave pairing induced by a Feshbach resonance and imposing the phase-equilibrium conditions for the phase-separated state. The imbalance chemical potential is chosen to be smaller than the energy gap, so that other possible phases are avoided in the regime considered here. The energy gap and Hartree Fock potentials are obtained self- consistently. The effects of interaction strength and mass ratio on the phase diagram, superfluid density of states, and quasiparticle specific heat are then examined. Within the investigated parameter range, increasing the magnitude of the interaction strength increases the average and imbalance chemical potentials, while reducing the energy gap and the superfluid density of states. The total quasiparticle specific heat decreases with increasing imbalance chemical potential and interaction strength, but increases with mass ratio. Results for the Fermi Fermi mixture of dysprosium and potassium atoms show that the specific heat provides a thermal signature of mass-asymmetric pairing.