Bulk evidence for single-gap s-wave superconductivity in the intercalated graphite superconductor C$_6$Yb

TL;DR

This study provides strong evidence that the intercalated graphite superconductor C$_6$Yb exhibits single-gap s-wave superconductivity, based on thermal conductivity and resistivity measurements at very low temperatures.

Contribution

The paper presents experimental evidence confirming the s-wave nature of superconductivity in C$_6$Yb, ruling out multi-gap or unconventional pairing mechanisms.

Findings

Residual thermal conductivity shows exponential suppression, indicating a fully gapped s-wave superconductor.

Results rule out multi-gap or unconventional superconductivity in C$_6$Yb.

Measurements support a single-gap s-wave superconducting order parameter.

Abstract

We report measurements of the in-plane electrical resistivity $\rho$ and the thermal conductivity $\kappa$ of the intercalated graphite superconductor C$_6$Yb to temperatures as low as $T_c$/100. When a field is applied along the c-axis, the residual electronic linear term $\kappa_0/T$ evolves in an exponential manner for $H_{c1} < H < H_{c2}$. This activated behaviour establishes the order parameter as unambiguously s-wave, and rules out the possibility of multi-gap or unconventional superconductivity in this system.