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