Anelastic relaxation in the high-TcsuperconductorYBa2Cu3O7−x

The first measurement of anelastic relaxation in a vibrating sample of YBa/sub 2/Cu/sub 3/O/sub 7-//sub x/ is reported. A marked drop in the dissipation is observed below T/sub c/, from which a strong electron-phonon interaction is inferred. It is found that the Bardeen-Cooper-Schrieffer theory with a gap of ..delta../k/sub B/ = 240 K can explain this drop. The data also suggest the occurrence of a phase transition at 235 K.