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 in the BCS-BEC crossover, we present a Kubo-based microscopic calculation of thermal conductivity kappa, 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 drops upon crossing the pseudogap temperature T^*, and its temperature dependence changes below T_c. The drops become more pronounced on the weakly coupled BCS side, where the Pauli blocking causes the upturn of kappa above T^*. Our calculations fit well with the sound measurement on the damping rate.
Highlights
Recent experiments on sound waves in a unitary Fermi gas reveal many transport properties about strongly interacting fermions
Based on the pseudogap theory, our calculation addresses into the superfluid phase, which gives higher results of κ than the kinetic calculations based on phonons
We consider primarily the fermionic contributions to the thermal transport, which may be the dominant thermal carriers in the weak dissipation regions where the relaxation rate of the system is relatively smaller than the characteristic energy scales
Summary
Recent experiments on sound waves in a unitary Fermi gas reveal many transport properties about strongly interacting fermions. Several experiments have explored the damping rate of sound waves from the density response function[14,16,17], which contains both the contributions of momentum and temperature gradients related to the shear and bulk viscosities and thermal conductivity, respectively.
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