The high-field phase diagram of the cuprates derived from the Nernst effect

TL;DR

This study uses Nernst effect measurements to map the high-field phase diagram of cuprates, revealing that phase coherence is lost at a temperature higher than the zero-field critical temperature, indicating a phase fluctuation-driven transition.

Contribution

It demonstrates that the upper critical field extends beyond the zero-field critical temperature, suggesting phase rigidity loss rather than pairing amplitude disappearance as the transition mechanism.

Findings

Vorticity persists up to very high fields near $T_{c0}$

The $H_{c2}(T)$ curve ends at a temperature above $T_{c0}$

An intermediate field $H^*(T)$ governs flux-flow resistivity.

Abstract

Measurements of the Nernst signal in the vortex-liquid state of the cuprates to high fields (33 T) reveal that vorticity extends to very high fields even close to the zero-field critical temperature $T_{c0}$. In overdoped $\rm La_{2-x}Sr_xCuO_4$ (LSCO) we show that the upper critical field $H_{c2}(T)$ curve does not end at $T_{c0}$, but at a much higher temperature. These results imply that $T_{c0}$ corresponds to a loss in phase rigidity rather than a vanishing of the pairing amplitude. An intermediate field $H^*(T)\ll H_{c2}(T)$ is shown to be the field scale for the flux-flow resistivity.