Nodeless Superconductivity in the Noncentrosymmetric Superconductor $Mg_{10}Ir_{19}B_{16}$

摘要

We measured the resistivity, diamagnetization and low temperature specificheat of the newly discovered noncentrosymmetric superconductor$Mg_{10}Ir_{19}B_{16}$. It is found that the superconducting gap has an s-wavesymmetry with a value of about $\Delta_0 \approx$ 0.6 meV, and the ratio$\Delta_0/k_BT_c\approx1.86$ indicates a weak coupling for thesuperconductivity. The correlations among the normal state Sommerfeld constant$\gamma_n$, the slope $-d\mu_0H_{c2}(T)/dT$ near Tc and the condensation energyEc are all consistent with the weak coupling picture. The separated phononcontribution from the specific heat shows that the conduction electrons of the$Ir$ atoms interact most strongly with the vibrations of themselves, instead ofwith that of the light element boron.