Origin of the maximal critical temperature disparities in one-layer cuprate superconductors

TL;DR

This paper investigates the factors influencing the maximum critical temperature in one-layer cuprate superconductors, emphasizing the role of Fermi surface topology and material parameters beyond just apical oxygen distance.

Contribution

It introduces a weak coupling model linking Tcmax to Fermi surface topology and material parameters, explaining disparities in critical temperatures among cuprates.

Findings

Tcmax peaks near the Lifshitz transition from open to closed Fermi surface.

Material parameters like hopping amplitudes and Coulomb repulsion significantly affect Tcmax.

Analytic expressions for Tcmax are derived near and away from criticality.

Abstract

Recently a phonon exchange d - wave pairing mechanism in cuprates was proposed. The phonons are the lateral apical oxygen atoms vibrations. They generate the attractive pairing potential peaked at X point of the Brillouin zone, V (k) = exp [-2kda], where da is distance from the CuO planes. The model explains a rather paradoxical well known negative correlation of the optimal doping critical temperature Tcmax with da and increase of Tcmax with pressure. However the large disparities in Tcmax, especially in one - layer cuprate superconductors, from 39K for La2-xSrxCuO4, to 95K for HgBa2CuO4+x, cannot be attributed by differencies in da. Other important material parameters include the hopping amplitudes t; t0 and the on site Coulomb repulsion U. It is shown (within weak coupling)that Tcmax is highest for materials close to the topological (Lifshitz) transition from an open to a close Fermi surface. The transition occurss for t0 = -0.19t and rather small values of effective value of U = 2t at optimal doping. Analytic expressions for Tcmax are derived both near criticality and away from it.