Comparison of Resistivity and Superfluid Response in Thin CaYBCO Films

Resistivity drops to negligible levels at temperatures significantly above those at which superfluid density appears for two-dimensional samples of Ca-doped YBCO. The temperature offset between the disappearance of resistivity and the onset of superfluid density, as measured by low-frequency mutual inductance experiments, depends upon $T_c$ as measured by the appearance of superfluid density, getting bigger as $T_c$ decreases and reaching a maximum as superfluid response disappears near the superconductor-insulator transition while still exhibiting a resistive transition. The offset vanishes at the maximum $T_c$.