Field-enhanced diamagnetism in intense magnetic field in the pseudogap state of the cuprate $\rm Bi_2Sr_2CaCu_2O_{8+\delta}

TL;DR

This study reveals a field-enhanced diamagnetic response above the superconducting transition temperature in a cuprate, supporting the vortex scenario for phase coherence loss, with implications for understanding the pseudogap state.

Contribution

It provides experimental evidence of a field-enhanced diamagnetic signal above T_c in Bi-2212, supporting vortex-based explanations for the pseudogap phase.

Findings

Diamagnetic signal increases with magnetic field up to 32 Tesla

Signal scales with the Nernst effect, indicating vortex activity

Results support vortex scenario over amplitude fluctuations

Abstract

In hole-doped cuprates, Nernst experiments imply that the superconducting state is destroyed by spontaneous creation of vortices which destroy phase coherence. Using torque magnetometry on $\rm Bi_2Sr_2CaCu_2O_{8+\delta}$, we uncover a field-enhanced diamagnetic signal $M$ above the transition temperature $T_c$ that increases with applied field to 32 Tesla and scales just like the Nernst signal. The magnetization results above $T_c$ distinguish $M$ from conventional amplitude fluctuations, and strongly support the vortex scenario for the loss of phase coherence at $T_c$.