Nodal and nodeless gap in proximity-induced superconductivity: Application to monolayer CuO2 on a Bi2Sr2CaCu2O8+δ substrate.

We present a detailed analysis on the hopping between monolayer CuO2 and bulk CuO2 plane in the Bi2Sr2CaCu2O8+δ; substrate. With a two-band model, we demonstrate that the nodeless gap can only exist when the hole concentration in the monolayer CuO2 plane is very large. We argue that the possible phase separation may play an important role in the recent experimental observation of a nodeless gap. [ABSTRACT FROM AUTHOR]