The Josephson relation for the superfluid density in the BCS-BEC crossover

Abstract

The Josephson relation for the superfluid density is derived for a Fermi superfluid in the BCS-BEC crossover. This identity extends the original Josephson relation for Bose superfluids. It gives a simple exact relation between the superfluid density ${\rho }_s$ and the broken-symmetry Cooper pair order parameter ${\Delta }_0$ in terms of the infrared limit of the pair fluctuation propagator. The same expression holds through the entire BCS-BEC crossover, describing the superfluid density of a weak-coupling BCS superfluid as well as the superfluid density of a Bose condensate of dimer molecules.

Published version

References in corpus (5)

• Weakly bound dimers of fermionic atoms
• BCS-BEC crossover at finite temperature in the broken-symmetry phase
• Pairing fluctuations and the superfluid density through the BCS-BEC crossover
• Temperature of a trapped unitary Fermi gas at finite entropy
• Popov approximation for composite bosons in the BCS-BEC crossover