Competing ferromagnetism in high temperature copper oxide superconductors

TL;DR

This paper proposes that competing ferromagnetic fluctuations coexist with superconductivity in high-temperature cuprate superconductors, explaining puzzling phenomena in the overdoped regime and suggesting a quantum critical point beyond the superconducting dome.

Contribution

It introduces a theory that links ferromagnetic fluctuations to the phase diagram of cuprates, offering new explanations for the overdoped regime's properties.

Findings

Ferromagnetic fluctuations coexist with superconductivity in overdoped cuprates.

The superconducting dome terminates at a quantum critical point.

Predictions for new experiments to test ferromagnetic fluctuations.

Abstract

The extreme variability of observables across the phase diagram of the cuprate high temperature superconductors has remained a profound mystery, with no convincing explanation of the superconducting dome. While much attention has been paid to the underdoped regime of the hole-doped cuprates because of its proximity to a complex Mott insulating phase, little attention has been paid to the overdoped regime. Experiments are beginning to reveal that the phenomenology of the overdoped regime is just as puzzling. For example, the electrons appear to form a Landau Fermi liquid, but this interpretation is problematic; any trace of Mott phenomena, as signified by incommensurate antiferromagnetic fluctuations, is absent, and the uniform spin susceptibility shows a ferromagnetic upturn. Here we show and justify that many of these puzzles can be resolved if we assume that competing ferromagnetic fluctuations are simultaneously present with superconductivity, and the termination of the superconducting dome in the overdoped regime marks a quantum critical point beyond which there should be a genuine ferromagnetic phase at zero temperature. We propose new experiments, and make new predictions, to test our theory and suggest that effort must be mounted to elucidate the nature of the overdoped regime, if the problem of high temperature superconductivity is to be solved. Our approach places competing order as the root of the complexity of the cuprate phase diagram.