Cross-Interface Electron-Photon Interactions in FeSe Films on Oxide Substrates

Condensed Matter Seminars

Speaker: Steve Johnston, University of Tennessee
Date & Time: June 2, 2016, 2:00 - 3:00
Location: Hennings 318
Local Contact: Mona Berciu
Intended Audience: Graduate

A flurry of scientific activities has been generated by the discovery of a significantly enhanced superconductivity in ultra thin films of FeSe grown on oxide substrates such as SrTiO3 . At present there are two main groups of proposals for the origin of this enhancement: those involving excess electron doping by the substrate or those involving a more direct interaction between the substrate and the film. The latter has recently gained strong experimental support from the observation of replica bands in the electronic structure of FeSe/STO [1], which indicates coupling to an oxygen phonon mode in the substrate [2]. In this talk I will discuss several aspects of this scenario, including the unique momentum structure of this interaction, which is strongly peaked
in the forward scattering direction. I will show that such a coupling leads to departures from the expectations gleamed from conventional BCS theory and can account for the Tc enhancement in FeSe/STO. I will also discuss the implications of this scenario for other thin film systems.

[1] J. J. Lee et al., Nature 515, 245 (2014).

[2] L. Rademaker et al., NJP 18, 022001 (2016); Y. Wang et al., Supercond. Sci. Technol. 29, 054009 (2016).