Strong Phonon Effects in High-Transition-Temperature Superconductors

The high-transition-temperature superconducting compounds ${\mathrm{V}}_3$Ga and ${\mathrm{V}}_3$Si have a very large electronic specific heat and strong temperature-dependent susceptibility. These properties are interpreted in terms of a large electron-phonon enhancement of the density of states, and a large exchange enhancement of the susceptibility.