BCS temperature-dependent superconducting energy gap in domain boundaries of melt-textured YBa2Cu3O7

Attenuation and velocity measurements in low magnetic fields in the superconducting state of a melt-textured sample of YBa2Cu3O7 are reported. Changes in both attenuation α and relative velocity dv/v are observed at the penetration field H'c1 of its domain boundaries. The change in dv/v at H'c1 appears to be proportional to the repulsive force between vortices. The change in α at H'c1 may be produced by a relaxation process involving superconducting quasiparticles in the vicinity of the normal core of the vortices. Analysis of the relaxation time associated with this process yields a temperature-dependent energy gap which follows the BCS dependence. The relaxation time associated with the process is about 10-11 sec. 19 refs., 10 figs