The superconducting gap of \QTR{em}{in situ} $MgB_{2}$ thin films by microwave surface impedance measurements
arXiv:cond-mat/0212009 · doi:10.1063/1.1517181
Abstract
Precision measurements of the microwave surface resistance $R_{s}$ of in situ $MgB_{2}$ films directly reveal an exponential behavior of $R_{s}$ at low temperature indicating a fully-gapped order parameter. The entire temperature dependence of $R_{s}$ is well described by a Mattis-Bardeen formalism but with a small gap ratio of $Î(0)/kT_{c}=0.72$, corresponding to $Î(0)=1.9meV$.