Ubiquitous strong electron phonon coupling at the interface of FeSe/SrTiO3

TL;DR

This study demonstrates strong and ubiquitous electron-phonon coupling at the interface of FeSe and SrTiO3 surfaces, which likely enhances superconductivity across different surface orientations, as evidenced by ARPES measurements showing replica bands.

Contribution

It reveals that electron-phonon coupling at FeSe/SrTiO3 interfaces is a generic feature, present on both (001) and (110) surfaces, contributing to high-temperature superconductivity.

Findings

Replica bands observed on both STO(001) and STO(110) surfaces.

Electron-phonon coupling is a common feature of STO surfaces.

Enhanced superconducting gaps likely due to FeSe-STO phonon coupling.

Abstract

The high temperature superconductivity in single-unit-cell (1UC) FeSe on SrTiO3 (STO)(001) and the observation of replica bands by angle-resolved photoemission spectroscopy (ARPES) have led to the conjecture that the coupling between FeSe electron and the STO phonon is responsible for the enhancement of Tc over other FeSe-based superconductors1,2. However the recent observation of a similar superconducting gap in FeSe grown on the (110) surface of STO raises the question of whether a similar mechanism applies3,4. Here we report the ARPES study of the electronic structure of FeSe grown on STO(110). Similar to the results in FeSe/STO(001), clear replica bands are observed. We also present a comparative study of STO (001) and STO(110) bare surfaces, where photo doping generates metallic surface states. Similar replica bands separating from the main band by approximately the same energy are observed, indicating this coupling is a generic feature of the STO surfaces and interfaces. Our findings suggest that the large superconducting gaps observed in FeSe films grown on two different STO surface terminations are likely enhanced by a common coupling between FeSe electrons and STO phonons.