Correlation Induced Vanishing of the Gap Function on the Fermi Surface in High $T_c$ Superconductors

TL;DR

This paper demonstrates through physical arguments and numerical evidence that the superconducting gap function vanishes on the Fermi surface in strongly correlated electron systems like the Hubbard and t-J models, challenging conventional expectations.

Contribution

It provides the first numerical evidence showing the vanishing of the gap function on the Fermi surface in strongly correlated models using exact diagonalization.

Findings

Gap function vanishes on the Fermi surface in studied models

Numerical results obtained from small cluster exact diagonalization

Supports the correlation-induced suppression of the gap on the Fermi surface

Abstract

We present physical arguments as well as numerical evidence to show that the Cooper pair (gap) function vanishes on the Fermi surface in strongly correlated electron systems such as \tJ and \lU Hubbard models in one and two dimensions. Using exact diagonalization, we study a correlation function which is a measure of the gap function even in a finite system, and present numerical results for this correlation function on small clusters of 8 (Hubbard) and 16 ($t-J$) sites.