Electron heat capacity and moments of the phonon density of states for metals and superconductors

A technique for determining the electron heat capacity constant γ for metals and superconductors is suggested that also allows one to determine the second and the fourth moments of the phonon density of states g(ω) with high accuracy. The method is based on a high-temperature expansion of a lattice heat capacity. All terms of the expansion are taken into account. From experimental heat-capacity results both the lattice and the electron characteristics of ${\mathrm{TmBa}}_2$ ${\mathrm{Cu}}_3$ ${\mathrm{O}}_7$ high-temperature superconducting ceramics have been extracted.