Unusual Nernst effect suggestive of time-reversal violation in the striped cuprate La$_{2-x}$Ba$_x$CuO$_4$

TL;DR

This study reports a large, symmetric Nernst signal in striped cuprate La$_{2-x}$Ba$_x$CuO$_4$ below charge-ordering temperature, indicating possible time-reversal symmetry violation and spontaneous vortex creation.

Contribution

It provides evidence of time-reversal violation through an anomalous Nernst effect in a specific cuprate superconductor, suggesting novel vortex phenomena.

Findings

Large, symmetric Nernst signal below $T_{co}$

Signal persists as magnetic field approaches zero

Indicates spontaneous vortex creation and time-reversal violation

Abstract

The striped cuprate La$_{2-x}$Ba$_x$CuO$_4$ ($x=\frac18)$ undergoes several transitions below the charge-ordering temperature $T_{co}$ = 54 K. From Nernst experiments, we find that, below $T_{co}$, there exists a large, anomalous Nernst signal $e_{N,even}(H,T)$ that is symmetric in field $H$, and remains finite as $H\to 0$. The time-reversal violating signal suggests that, below $T_{co}$, vortices of one sign are spontaneously created to relieve interlayer phase frustration.