  We investigate the hydrostatic pressure dependence of interfacial
superconductivity occurring at the atomically sharp interface between two
non-superconducting materials: the topological insulator (TI) Bi2Te3 and the
parent compound Fe1+yTe of the chalcogenide iron based superconductors. Under
pressure, a significant increase in the superconducting transition temperature
Tc is observed. We trace the pressure dependence of a superconducting twin gap
structure by Andreev reflection point contact spectroscopy (PCARS), which shows
that a large superconducting gap associated with the interfacial
superconductivity increases along with Tc. A second smaller gap, which is
attributed to proximity-induced superconductivity in the TI layer, increases
first, but then reaches a maximum and appears to be gradually suppressed at
higher pressure. We interpret our data in the context of a pressure-induced
doping effect of the interface, in which charge is transferred from the TI
layer to the interface and the interfacial superconductivity is enhanced. This
demonstrates the important role of the TI in the interfacial superconductivity
mechanism.
