STUDY OF THE SUPERCONDUCTING ORDER-PARAMETER IN ZN BY POINT-CONTACT SPECTROSCOPY

The temperature T and magnetic field B dependence of the superconducti ng order parameter Delta and DOS broadening parameter Gamma in Zn were evaluated from the measured differential resistance dV/dI vs. voltage V of Zn-Ag point contacts (PC) using the modified BTK theory. The Del ta(T) of all PC follows BCS theory while Delta(B) shows both a first-o rder transition at B-c(PC) < B-c(bulk) for some PC and continuous decr ease of Delta(B) to zero at B-c(PC) >> B-c(bulk). The Gamma is almost independent of B in the first case in contrast to the increase with a B in the second case. Moreover, in zero field Gamma increases with PC resistance.