SCALING OF THE SUPERCONDUCTING ORDER-PARAMETER IN BI CUPRATES WITH T-C

Tunneling measurements have been carried out by the point-contact tech nique on four members of the Bi cuprates: on the (Bi,Pb)(2)Sr2Ca2Cu3O1 0+x (2223), Bi2Y0.1Sr1.9CaCu2O8+x (Y2212), Bi2.1Sr1.9CaCu2O8+x (2212) superconductors at 4.2 K and on Bi2.07Sr1.8CuO6+x (2201) at 2 K. The p olycrystalline samples have the critical temperature T-c = 108 K, 94 K , 85 K and 7 K, respectively. All measured tunneling spectra (tunnelin g conductance versus the bias voltage) reveal a significant reduction below a certain voltage indicating the superconducting gap edge. The B CS-like formula for the superconducting density of states accounting f or some additional smearing can successfully fit the experimental data , particularly at the gap position. Discrepancies found at lower volta ges inside the gap may indicate a possible anisotropy of the order par ameter, but an extrinsic origin (like inhomogenity in the sample, irre gularities in the tunnel barrier) is possible as well. The obtained va lues of the reduced superconducting energy gap 2 Delta/k(B)T(c) amount to 6-7 for all four systems. Consequently, our results found the gap Delta scaling with the transition temperature T-c in the Bi cuprates.