CMT Seminar: Alex Aperis

Interface-induced high-Tc superconductivity in monolayer FeSe/SrTiO₃

When a monolayer of FeSe is deposited on SrTiO₃, the superconducting critical temperature jumps from the bulk Tc=8 K to typical values of Tc=50-70 K and up to Tc=100 K. ARPES measurements indicate that an interface-induced electron-phonon interaction between FeSe electrons and SrTiO₃ phonons plays a decisive role in this phenomenon. However, the coupling to these phonons is considered too weak to fully explain the high-Tc in this system which therefore remains under intensive research.

We have examined the impact of such phonons on the superconducting state of FeSe/SrTiO₃ developing multiband, full bandwidth, anisotropic Eliashberg theory. In this talk, I will discuss some of our recent findings including strong evidence in favour of the interfacial phonons being the main mediators of the high-Tc, the implications of Cooper pairing away from the Fermi level and predictions for experimental signatures of this mechanism. Furthermore, I will present our self-consistently calculated temperature dependent ARPES and tunnelling spectra for this system and discuss how recent puzzles like the superconducting gap anisotropy seen by ARPES and the low-energy boson signatures observed in the tunnelling spectra can be explained within our picture.