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

Abstract

The striped cuprate La${}_{2-x}$Ba${}_x$CuO${}_4$ ($x=\frac{1}{8})$ 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.

5 pages, 4 figures