Muon Spin Relaxation Studies of Superconductivity in a Crystalline Array of Weakly Coupled Metal Nanoparticles

TL;DR

This study uses Muon Spin Relaxation to demonstrate bulk type II superconductivity in a crystalline metal nanoparticle compound below 7.8 K, revealing weak electron-phonon coupling and providing insights into its conduction mechanism.

Contribution

First Muon Spin Relaxation analysis of superconductivity in a crystalline metal nanoparticle array, showing type II behavior and weak coupling characteristics.

Findings

Superconductivity observed below 7.8 K with specific critical fields.

Data consistent with s-wave BCS model with weak electron-phonon coupling.

Weak flux pinning observed in the superconductor.

Abstract

We report Muon Spin Relaxation studies in weak transverse fields of the superconductivity in the metal cluster compound, Ga$\_{84}$[N(SiMe$\_{3}$)$\_{2}$]$\_{20}$-Li$\_{6}$Br$\_{2}$(thf)$\_{20}\cdot $2toluene. The temperature and field dependence of the muon spin relaxation rate and Knight shift clearly evidence type II bulk superconductivity below $T\_{\text{c}}\approx7.8$ K, with $B\_{\text{c1}}\approx 0.06$ T, $B\_{\text{c2}}\approx 0.26 $ T, $\kappa\sim 2$ and weak flux pinning. The data are well described by the s-wave BCS model with weak electron-phonon coupling in the clean limit. A qualitative explanation for the conduction mechanism in this novel type of narrow band superconductor is presented.