Testing for pair-density-wave order in La$_{1.875}$Ba$_{0.125}$CuO$_4$

TL;DR

This study investigates the existence of pair-density-wave order in La$_{1.875}$Ba$_{0.125}$CuO$_4$ by measuring critical currents and finds results inconsistent with PDW predictions, suggesting a different superconducting phase.

Contribution

The paper provides the first experimental test for PDW order in a cuprate superconductor, challenging previous theoretical predictions.

Findings

Critical current variation does not match PDW model predictions.

Evidence suggests a minority phase of $d$-wave superconductivity.

Charge inhomogeneity may influence superconducting properties.

Abstract

Charge order is commonly believed to compete with superconducting order. An intertwined form of superconducting wave function, known as pair-density-wave (PDW) order, has been proposed; however, there has been no direct evidence, theoretical or experimental, that it forms the ground state of any cuprate superconductor. As a test case, we consider \lbco\ with $x=1/8$, where charge and spin stripe orders within the CuO$_2$ planes compete with three-dimensional superconducting order. We report measurements of the superconducting critical current perpendicular to the planes in the presence of an in-plane magnetic field. The variation of the critical current with orientation of the field is inconsistent with a theoretical prediction specific to the PDW model. It appears, instead, that the orientation dependence of the critical-current density might be determined by a minority phase of $d$-wave superconductivity that is present as a consequence of doped-charge inhomogeneity.