Sharp k-space features in the order parameter within the interlayer pair-tunneling mechanism of high-Tc superconductivity

Abstract

We study the k dependence of the gap function of a bilayer superconductor, using standard mean-field techniques applied to a two-dimensional 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 pair tunneling into the effective pairing potential leads to highly nontrivial 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.

Source-reported materials — not catalogue approval

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