Establishing the Presence of Coherence in Atomic Fermi Superfluids: Spin-Flip and Spin-Preserving Bragg Scattering at Finite Temperatures

摘要

We show how the difference between the finite temperature T structurefactors, called S_-, associated with spin and density, can be used as aindication of superfluidity in ultracold Fermi gases. This observation can beexploited in two photon Bragg scattering experiments on gases which undergoBCS- Bose Einstein condensation crossover. Essential to our calculations is aproper incorporation of spin and particle number conservation laws which leadto compatibility at general T with two f-sum rules. Because it is applicable togeneral scattering lengths, a measurement of S- can be a useful, directapproach for establishing where superfluidity occurs.