Two types of superconducting pairs in stripe-ordered La$_{2-x}$Ba$_{x}$CuO$_4$ ($x=1/8$): evidence from the resistivity measurements

TL;DR

This paper presents evidence for two distinct types of superconducting pairs in stripe-ordered La$_{2-x}$Ba$_x$CuO$_4$ ($x=1/8$), based on resistivity measurements and theoretical modeling, revealing complex pairing mechanisms.

Contribution

It introduces the concept of two different superconducting pair types in stripe-ordered LBCO, supported by resistivity data and a theoretical model explaining their behavior.

Findings

Existence of two superconducting pair types with different properties.

Exponential temperature dependence of c-axis resistivity indicating phase slips.

A theoretical fit for the magnetic field dependence of resistivity.

Abstract

Recent angle-resolved $c$-axis resistivity measurements of the stripe-ordered La$_{2-x}$Ba$_x$CuO$_4$ (LBCO) with $x=1/8$ revealed an unexpected dependence on the direction of the in-plane magnetic field. We argue that these and other available data for the $c$-axis transport point to the existence of superconducting pairs of two different types in the $x=1/8$ LBCO below the stripe ordering temperature. The pairs of one type carry finite momentum and are confined to the Cu-O planes; the pairs of other type (probably the conventional $d$-wave with zero momentum) propagate along narrow conducting channels traversing the sample in the $c$-axis direction. The evidence for this comes from the observed exponential temperature dependence of the $c$-axis resistivity $\rho_c(T)$ which we attribute to the thermally excited slips of the superconducting phase and flux flows. We present a simple theory to fit the observed $\pi/2$-periodic dependence of $\rho_c$ on the direction of the in-plane magnetic field and the other data.