Repository logo
 

Understanding and enhancing superconductivity in FeSe/SrTiO$_3$ by quantum size effects

Accepted version
Peer-reviewed

Type

Article

Change log

Authors

Murta, B 
Garcia Garcia, AM 

Abstract

Superconductivity in one-atom-layer iron selenide (FeSe) on a strontium titanate (STO) substrate is enhanced by almost an order of magnitude with respect to bulk FeSe. There is recent experimental evidence suggesting that this enhancement persists in FeSe/STO nanoislands. More specifically, for sizes L ~ 10 nm, the superconducting gap is a highly nonmonotonic function of L with peaks well above the bulk gap value. This is the expected behavior only for weakly-coupled metallic superconductors such as Al or Sn. Here we develop a theoretical formalism to describe these experiments based on three ingredients: Eliashberg theory of superconductivity in the weak coupling limit, pairing dominated by forward scattering, and periodic orbit theory to model spectral fluctuations. We obtain an explicit analytical expression for the size dependence of the gap that describes quantitatively the experimental results with no free parameters. This is a strong suggestion that superconductivity in FeSe/STO is mediated by STO phonons. We propose that, since FeSe/STO is still a weakly coupled superconductor, quantum size effects can be used to further enhance the bulk critical temperature in this interface.

Description

Keywords

cond-mat.supr-con, cond-mat.supr-con, cond-mat.mes-hall

Journal Title

Physical Review B - Condensed Matter and Materials Physics

Conference Name

Journal ISSN

2469-9950
2469-9969

Volume Title

94

Publisher

American Physical Society
Sponsorship
Engineering and Physical Sciences Research Council (EP/I004637/1)