Density Fluctuation Mediated Superconductivity

TL;DR

This paper compares mean-field predictions of density fluctuation-mediated superconductivity in cubic and tetragonal lattices, highlighting increased robustness in lower dimensions and sensitivity to ordering wavevectors.

Contribution

It introduces a mean-field framework for density fluctuation-mediated pairing, emphasizing the effects of lattice anisotropy and incipient ordering on superconductivity.

Findings

Density fluctuation pairing is more robust in quasi-two dimensions.

Robustness increases with lattice anisotropy from cubic to tetragonal.

Sensitivity of pairing robustness to the incipient ordering wavevector.

Abstract

We conpare predictions of the mean-field theory of supercnductivity for metallic systems on the border of a density instability for cubic and tetragonal lattices. The calculations are based on a parametrisation of an effective interaction arising from the exchange of density fluctuations and assume that a single band is relevant for superconductivity. The results show that for comparable model parameters, desnity fluctuation mediated pairing is more robust in quasi-two dimensions than in three dimensions, and that the robustness of pairing increases gradually as one goes from a cubic to a more and more anisotropic tetragonal structure. We also find that the robustness of density fluctuation mediated pairing can depend sensitively on the incipient ordering wavevector. We discuss the similarities and differences between the mean-field theories of superconductivity for density and magnetically mediated pairing.