Signatures of pair-density wave order in phase-sensitive measurements of La_2-xBa_xCuO₄-Nb Josephson junctions and SQUIDs

2018/11/05 by Hamilton, D. R., Gu, G. D., Fradkin, E. +1
#FOS: Physical sciences #Superconductivity (cond-mat.supr-con)

paper · doi:10.48550/arxiv.1811.02048

Abstract

The interplay of charge order, spin order, and superconductivity in La_2-xBa_xCuO₄ creates a complex physical system that hosts several interesting phases, such as two-dimensional superconductivity within the CuO₂ planes and the ordered pair-density wave state in which charge ordering is intertwined with superconductivity. Using Josephson interferometry techniques, we measure the current-phase relation of junctions and SQUIDs incorporating this material and observe a significant sin(2ϕ)-component indicative of closely-spaced alternations of the sign of the Josephson coupling predicted by the pair-density wave model. We find that the ratio of the sin(2ϕ)-component to the conventional sin(ϕ)-component to be largest near x=1/8 doping, where the pair-density wave state is believed to be the strongest, and that it increases with increasing temperature as the Josephson coupling in the junction weakens.

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