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 alpha 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 alpha 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.