Theoretical Approach to the Gauge Invariant Linear Response Theories for Ultracold Fermi Gases with Pseudogap. (1st October 2015)

• Record Type: Journal Article
• Authors: Guo, Hao; He, Yan
• Other Names: Durajski Artur P. Academic Editor.
• Is Part Of: Advances in condensed matter physics. Volume 2015(2015)
• Publication Date: 2015-10-01
• Subjects: Condensed matter -- Periodicals; Condensed matter; Periodicals; 530.41
• DOI: 10.1155/2015/582734
• Languages: English
• ISSNs: 1687-8124

Abstract

Abstract : Recent experimental progress allows for exploring some important physical quantities of ultracold Fermi gases, such as the compressibility, spin susceptibility, viscosity, optical conductivity, and spin diffusivity. Theoretically, these quantities can be evaluated from suitable linear response theories. For BCS superfluid, it has been found that the gauge invariant linear response theories can be fully consistent with some stringent consistency constraints. When the theory is generalized to stronger than BCS regime, one may meet serious difficulties to satisfy the gauge invariance conditions. In this paper, we try to construct density and spin linear response theories which are formally gauge invariant for a Fermi gas undergoing BCS-Bose-Einstein Condensation (BEC) crossover, especially below the superfluid transition temperatureT c . We adapt a particulart -matrix approach which is close to theG 0 G formalism to incorporate noncondensed pairing in the normal state. We explicitly show that the fundamental constraints imposed by the Ward identities andQ -limit Ward identity are indeed satisfied.