Critical behavior of the specific heat in Ti-Si amorphous alloys at the metal-insulator transition

In this paper, we report the measurements of specific heat of an amorphous Ti9.5Si90.5 alloy located very close to the critical point of the metal-insulator transition. In the presence of a magnetic field, the specific heat is dominated by the Schottky anomaly caused by magnetic moments associated with the dangling bonds in the matrix of amorphous Si. Subtraction of this contribution exposes the behavior of the electronic specific heat coefficient gamma. The coefficient is temperature independent above 2 K and is, in order of magnitude, close to the value expected in the absence of electron-electron interactions. In the temperature range 0.4-1.5 K, the coefficient gamma shows an anomalous downturn, which can be approximated by the dependence gamma(T) = gamma 0ln(T/T0), with T0 approximate to 0.2 K. In a companion paper, we found that the Hall coefficient in Ti-Si alloys is affected by the electron -electron interaction up to much higher temperature of 150 K and also varies critically across the metal-insulator transition. We compare our results with theoretical predictions for three models, which can potentially explain the anomalous behavior of the specific heat: generalized nonlinear a model, Coulomb glass, and many-body localization.