Thermal conductivity of an ultracold Fermi gas in the BCS-BEC crossover

Abstract

Abstract Recent experiments on sound waves in a unitary Fermi gas reveal many transport properties about strongly interacting fermions. Sound propagates through the coupling of momentum and heat transport, and attenuates strongly with the presence of a phase transition. In this work, focusing on the temperature regimes near and below the superfluid critical temperature $$T_c$$ T c in the BCS-BEC crossover, we present a Kubo-based microscopic calculation of thermal conductivity $$\kappa$$ κ , which has not attracted much attention compared to the shear viscosity. Our approach primarily addresses the contributions of the fermionic quasiparticles to thermal transport and our results return to the kinetic descriptions at high temperatures. $$\kappa$$ κ drops upon crossing the pseudogap temperature $$T^*$$ T ∗ , and its temperature dependence changes below $$T_c$$ T c . The drops become more pronounced on the weakly coupled BCS side, where the Pauli blocking causes the upturn of $$\kappa$$ κ above $$T^*$$ T ∗ . Our calculations fit well with the sound measurement on the damping rate.