Rigid-Band Behavior in the Specific Heats of PbTl and PbBi Alloys: Electron-Phonon Enhancement Effects

Abstract

The normal-state specific heats of pure lead and four dilute PbTl and PbBi alloys have been measured in the temperature range 1.0-2.3 K. The fractional rate of change of the electronic specific-heat coefficient $\gamma$ with respect to the number of conduction electrons per atom was found to be 0.25±0.06 for PbTl alloys and 0.51±0.04 for PbBi alloys. When changes in the electron-phonon enhancement factor as determined from tunneling measurements are included, good agreement is found between the measured changes in $\gamma$ and those expected from the rigid-band model. Semiquantitative calculations indicate that changes in the electron-phonon enhancement factor may also account for the apparent discrepancy between previous experimental results and the rigid-band model in noble-metal alloys. The Debye temperature was found to decrease for both lead alloy series.