Multiple Broken Symmetries in Striped La$_{2-x}$Ba$_{x}$CuO$_{4}$ detected by the Field Symmetric Nernst Effect

TL;DR

This study uses the field-symmetric Nernst effect to explore the interplay of stripe order, charge order, and superconductivity in La$_{2-x}$Ba$_{x}$CuO$_{4}$, revealing symmetry-breaking phenomena and charge ordering signatures.

Contribution

It provides new thermoelectric evidence of multiple broken symmetries and charge order in cuprates, linking these to stripe phases and superconductivity.

Findings

Detection of a sharp peak at charge order temperature $T_{CO}$

Evidence of time-reversal symmetry breaking above $T_c$

Observation of spontaneously generated vortices before superconductivity

Abstract

We report on a thermoelectric investigation of the stripe and superconducting phases of the cuprate La$_{2-x}$Ba$_{x}$CuO$_{4}$ near the $x=1/8$ doping known to host stable stripes. We use the doping and magnetic field dependence of field-symmetric Nernst effect features to delineate the phenomenology of these phases. Our measurements are consistent with prior reports of time-reversal symmetry breaking signatures above the superconducting $T_{{\rm c}}$, and crucially detect a sharp, robust, field-invariant peak at the stripe charge order temperature, $T_{{\rm {\scriptscriptstyle CO}}}$. Our observations suggest the onset of a nontrivial charge ordered phase at $T_{{\rm {\scriptscriptstyle CO}}}$, and the subsequent presence of spontaneously generated vortices over a broad temperature range before the emergence of bulk superconductivity in LBCO.