Enhancement of electron-phonon interactions in the nonequilibrium solid solutions Al1-xSix.

Abstract

We report unusual behavior of the low-temperature electrical resistivity $\ensuremath{\rho}$ of nonequilibrium substitutional solid solutions of the form ${\mathrm{Al}}_{1\ensuremath{-}x}{\mathrm{Si}}_{x}$. 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 ${L}_{\mathrm{I}\mathrm{I}\ensuremath{-}\mathrm{I}\mathrm{I}\mathrm{I}}$ 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 \ensuremath{\sim}11 K in ${\mathrm{Al}}_{1\ensuremath{-}x}{\mathrm{Si}}_{x}$ when $x=0.2$.