Magnetic-Field Dependence of the Energy Gap in Bi_2Sr_2CuO_(6+#delta#)

摘要

The electron-tunneling technique has been applied to study the magnetic-field effects of the energy gap in Bi_2Sr_2CuO_(6+#delta#). The measurements were carried out using break junction with ceramic samples having the critical temperature T_c = 6 K. By applying the field at 2 K, the gap structure disappears at approx approx 2-2.5 T, but in some junctions it survives up to at much higher fields. This difference probably reflects the geometrical effects at the junction. We have evaluated the field dependence of the pair-breaking parameter, which is consistent with that for the bulk type-II BCS superconductor in the vortex state.