Temperature and field dependence of the gap structure in Bi2Sr2CaCu2O8+δ studied by short-pulse interlayer tunneling spectroscopy

We measure tunneling characteristics of Bi2Sr2CaCu2O8+δ intrinsic junctions by a sub-microsecond pulse technique to investigate temperature T and the magnetic field H dependence of the bulk-intrinsic gap structure without excess Joule heating. The conductance curve shows a peak at the superconducting gap voltage (Vp) at low temperatures, and the peak becomes broader when we increase either T or H that is a pair breaking parameter. However, Vp has a non-monotonic T-dependence with a dip near Tc, while Vp increases monotonically with H. This difference indicates that Vp(T) cannot be explained in terms of a single gap model, and implies that the superconducting gap is distinct from the pseudogap, which is represented by Vp(T) above Tc