Superconductivity out of a non-Fermi liquid: Free energy analysis

Article

关键词: STRONG-COUPLING LIMIT;    STATE;    TRANSITION;   

DOI  :  10.1103/PhysRevB.106.144513

来源: SCIE

【 摘 要 】

In this paper, we present an in-depth analysis of the condensation energy E-c for a superconductor in a situation when superconductivity emerges out of a non-Fermi liquid due to pairing mediated by a massless boson. This is the case for electronic-mediated pairing near a quantum-critical point in metal, for pairing in SYK-type models, and for phonon-mediated pairing in the properly defined limit, when the dressed Debye frequency vanishes. We consider a subset of these quantum-critical models, in which the pairing in a channel with a proper spatial symmetry is described by an effective 0 + 1 dimensional model with the effective dynamical interaction V (Omega(m)) = (g) over bar/vertical bar Omega(m)vertical bar(gamma), where gamma is model-specific (the gamma model). In previous papers, we argued that the pairing in the. model is qualitatively different from that in a Fermi liquid, and the gap equation at T = 0 has an infinite number of topologically distinct solutions, Delta(n)(omega(m)), where an integer n, running between 0 and infinity, is the number of zeros of Delta(n)(omega(m)) on the positive Matsubara axis. This gives rise to the set of extrema of E-c at E-c,E-n, of which E-c,E-0 is the global minimum. The spectrum E-c,E-n is discrete for a generic gamma < 2 but becomes continuous at. = 2-0. Here, we discuss in more detail the profile of the condensation energy near each Ec, n and the transformation from a discrete to a continuous spectrum at gamma -> 2. We also discuss the free energy and the specific heat of the gamma model in the normal state.

【 授权许可】

Free