K-Space Gap Anisotropy within the Interlayer Pair-Tunneling Mechanism of High-T C Superconductivity

Abstract

We study the k-dependence of the gap function of a bilayer superconductor, using standard meanfield techniques applied to a two-dimensional (2D) extended Hubbard model, in the presence of coherent interlayer pair-tunneling and quenched coherent single-particle tunneling. The intralayer pairing potential thus defined is expandable in a finite number (5) of basis functions for the irreducible representations of the point-group of the perfectly square lattice, C4v. This gives rise to a competition between s-and d-wave symmetry, as the chemical potential is increased from the bottom to the top of a realistic band for most cuprates. It allows for mixed-symmetry paired state at temperatures below Tc, but never at Tc on a square lattice. Inclusion of the interlayer pairtunneling into the effective pairing potential leads to highly non-trivial k-space structures, such as pronounced maxima along the Fermi line not seen in the absence of interlayer pair-tunneling. We show how such a gap structure evolves with temperature and with band filling, and how it affects various observables. In particular, a nonuniversal value of the normalized jump in the specific heat at Tc will be evidenced, at variance with the conventional universal BCS result. PACS numbers: 74.20.-z 74.80.Dm 74.72.Hs 74.25.Bt

Unusual thermoelectric behavior of packed crystalline granular metals

“…In huge contrast, studies of the electrical resistance R͑T͒ of inhomogeneous composites have been of continuing interest, 20,21 with much emphasis on low-temperature phenomena because of superconductivity [22][23][24] and tunneling effects; e.g., see Refs. 25-28 and references therein.…”