2009/03/17 by W. R. Schneider, Schneider, William, Vijay B. Shenoy +3 · 1 citation
Physics and Astronomy · #Cold Atom Physics and Bose-Einstein Condensates #Atomic and Subatomic Physics Research #Quantum, superfluid, helium dynamics
paper · pdf · doi:10.48550/arxiv.0903.3006
We present two exact results for singular features in the radio frequency intensity I(ω) for ultracold Fermi gases. First, in the absence of final state interactions, I(ω) has a universal high frequency tail Cω-3/2 for all many-body states, where C is Tan's contact. Second, in a normal Fermi liquid at T=0, I(ω) has a jump discontinuity of Z/(1 - m/m*), where Z is the quasiparticle weight and m^*/m the mass renormalization. We then describe various approximations for I(ω) in polarized normal gases. We show why an approximation that is exact in the n_\dn=0 limit, fails qualitatively for n\dn > 0: there is no universal tail and sum rules are violated. The simple ladder approximation is qualitatively correct for very small n\dn, but not quantitatively.