Multiple broken symmetries in stripedLa2−xBaxCuO4detected by the field-symmetric Nernst effect

We report a thermoelectric investigation of the stripe and superconducting phases of the cuprate ${\mathrm{La}}_{2\ensuremath{-}x}{\mathrm{Ba}}_x{\mathrm{CuO}}₄$ near $x=1/8$. We vary the doping and the magnetic field to identify features in the field-symmetric Nernst effect consistent with the reports of time-reversal symmetry breaking above the superconducting ${T}_{\mathrm{c}}$. Crucially, we further detect a field-invariant peak at the stripe charge order temperature, ${T}_{\mathrm{CO}}$. Our observations suggest the onset of a nontrivial charge ordered phase at ${T}_{\mathrm{CO}}$, and the subsequent presence of spontaneously generated vortices before the emergence of bulk superconductivity.