Nodeless superconductivity in noncentrosymmetric PbTaSe$_2$ single crystals

TL;DR

This study reveals that PbTaSe$_2$, a noncentrosymmetric superconductor with a topologically nontrivial band structure, exhibits conventional nodeless s-wave superconductivity with a fully gapped order parameter.

Contribution

The paper provides the first detailed experimental evidence of nodeless, conventional s-wave superconductivity in PbTaSe$_2$, a topologically nontrivial noncentrosymmetric compound.

Findings

Exponential temperature dependence of London penetration depth indicates nodeless gap.

Superfluid density fits well with a single band s-wave model.

Superconducting gap magnitude close to weak-coupling BCS value.

Abstract

We report an investigation of the superconducting order parameter of the noncentrosymmetric compound PbTaSe$_2$, which is believed to have a topologically nontrivial band structure. Precise measurements of the London penetration depth $\Delta\lambda(T)$ obtained using a tunnel diode oscillator (TDO) based method show an exponential temperature dependence at $T\ll T_c$, suggesting a nodeless superconducting gap structure. A single band s-wave model well describes the corresponding normalized superfluid density, with a gap magnitude of $\Delta(0)=1.85T_c$. This is very close to the value of $1.76T_c$ for weak-coupling BCS superconductors, indicating conventional fully-gapped superconductivity in PbTaSe$_2$.