Tunneling measurements of fluctuation effects near the superconductor to insulator transition

We present measurements of the temperature dependence of the tunneling dens ity of states near the Fermi energy, G(o)(T), and resistive transitions, R( T), of ultrathin PbBi films. Both R(T) and G(o)(T) broaden substantially ne ar the superconductor to insulator transition (SIT). The broadening in R(TI is not affected by the proximity of a ground plane suggesting that long ra nge Coulomb interactions are not important to the SIT. The results suggest that the transport properties of Alms near the SIT are influenced by fluctu ations in both the phase and the amplitude of the order parameter. We discu ss the data in terms of recent theories of the superconducting transition i n low superfluid density systems. (C) 1998 Elsevier Science Ltd. All rights reserved.