Interplay of the pseudogap and the BCS gap for heteropairs in 40 K- 6 Li mixture
P. Lipavský, Christophe Berthod
The description of heteropairs like 40 K- 6 Li near and in the superconducting state requires a fully self-consistent theory (see H anai R. and O hashi Y., Phys. Rev. A , 90 (2014) 043622). We derive analytic pseudogap Green's functions for the “normal” and superconducting states from the Luttinger-Ward theory with the T -matrix in the static separable approximation. The self-consistency in the closing loop of self-energy has two pronounced effects on the single-particle spectrum. First, the single-particle excitations decay before the asymptotic quasiparticle propagation is established, therefore the normal state is not a Fermi liquid. Second, the pseudogap has a V shape even for s -wave pairing. The V-shaped pseudogap and the U-shaped BCS gap interfere resulting in slope breaks of the gap walls and the in-gap states in the density of states. Various consequences of an incomplete self-consistency are demonstrated.
arXiv:1609.00240•Europhysics Letters (EPL)•Nov 1, 2016•0 citations