Enhancement of electron-phonon interactions in the nonequilibrium solid solutionsAl1−xSix

We report unusual behavior of the low-temperature electrical resistivity $\rho$ of nonequilibrium substitutional solid solutions of the form ${\mathrm{Al}}_{1-x}{\mathrm{Si}}_x$. This behavior is thought to be similar to anomalies in $\frac{d^{2}I}{d{V}^2}$ observed in the tunneling or point-contact spectra of metals in the presence of disorder, and to result from strong electron-phonon interactions. The resistivity data, along with low-temperature heatcapacity measurements and Al $L_{\mathrm{I}\mathrm{I}-\mathrm{I}\mathrm{I}\mathrm{I}}$ x-ray-emission spectroscopy and NMR Knight shift experiments, strongly suggest that an enhancement of the electron-phonon interactions due to lattice instabilities is the main reason for the dramatic increase in the superconducting transition temperature $T_c$ to ∼11 K in ${\mathrm{Al}}_{1-x}{\mathrm{Si}}_x$ when $x=0.2\mathrm{}$.