Evidence of cooperative effect on the enhanced superconducting transition temperature at the FeSe/SrTiO3 interface

Abstract At the interface between monolayer FeSe films and SrTiO 3 substrates the superconducting transition temperature (T c) is unexpectedly high, triggering a surge of excitement. The mechanism for the T c enhancement has been the central question, as it may present a new strategy for seeking out higher T c materials. To reveal this enigmatic mechanism, by combining advances in high quality interface growth, 16 O ↔ 18 O isotope substitution, and extensive data from angle resolved photoemission spectroscopy, we provide striking evidence that the high T c in FeSe/SrTiO 3 is the cooperative effect of the intrinsic pairing mechanism in the FeSe and interactions between the FeSe electrons and SrTiO 3 phonons. Furthermore, our results point to the promising prospect that similar cooperation between different Cooper pairing channels may be a general framework to understand and design high-temperature superconductors.