Phenomenological Models for the Gap Anisotropy of Bi-2212 as Measured by ARPES

TL;DR

This paper analyzes the momentum dependence of the superconducting gap in Bi-2212 using ARPES data, proposing a phenomenological anisotropic s-wave model that highlights the role of next-neighbor interactions.

Contribution

It introduces a phenomenological anisotropic s-wave gap model fitting ARPES data and discusses its implications for microscopic theories of high-temperature superconductivity.

Findings

The anisotropic s-wave model fits the ARPES gap data well.

Next-neighbor Cu-Cu interactions are important in the superconducting pairing.

Alternative interpretations of the gap measurements are considered.

Abstract

Recently, high resolution angle-resolved photoemission spectroscopy has been used to determine the detailed momentum dependence of the superconducting gap in the high temperature superconductor Bi-2212. In this paper, we first describe tight binding fits to the normal state dispersion and superlattice modulation effects. We then discuss various theoretical models in light of the gap measurements. We find that the simplest model which fits the data is the anisotropic s-wave gap $\cos(k_x)\cos(k_y)$, which within a one-band BCS frame- work suggests the importance of next near neighbor Cu-Cu interactions. Various alternative interpretations of the observed gap are also discussed, along with the implications for microscopic theories of high temperature superconductors.