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

• Published in: Physical review. B, Condensed matter Condensed matter, 1994-05, Vol.49 (18), p.13247-13250
• Main Author: Naumov, VN
• Format: Article
• Language: English
• ISSN: 0163-1829; 1095-3795
• DOI: 10.1103/PhysRevB.49.13247

A technique for determining the electron heat capacity constant gamma 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( omega ) 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 TmBa sub 2 Cu sub 3 O sub 7 high-temperature superconducting ceramics have been extracted. conventional superconductor amorphous (a) Mo sub 3 Si. In the Ohmic regimes, rho sub xy is qualitatively similar to that observed in the high-T sub c superconductors. It changes sign near T sub c , and the sign change persists until both rho sub xy and rho sub xx becomes immeasurably small at T approx 0.8 T sub c (H). At current densities above the depinning current density, the Hall anomaly persists at low temperatures T approx 0.2 T sub c (H). This is contrary to a theory by Ferrell which attributes the anomaly to the backflow of thermally excited quasiparticles. In addition a model proposed by Harris, Ong, and Yan explains the anomaly as an effect arising from the layered nature of the high-T sub c cuprates. This model, however, does not explain the anomaly in a-Mo sub 3 Si which is an isotropic unlayered material. Osmium is discussed.