Interface high-temperature superconductivity

TL;DR

This paper reviews recent experimental advances in interface-enhanced high-temperature superconductivity, focusing on ultrathin films like FeSe on SrTiO3, and explores how interfaces influence superconducting properties and pairing mechanisms.

Contribution

It provides a comprehensive review of experimental progress on interface-enhanced superconductivity in ultrathin films, highlighting the significance of interfaces in raising transition temperatures.

Findings

Observation of interface-enhanced superconductivity in ultrathin films

Discovery of high Tc in 1UC-FeSe/STO with a ~20 meV gap

Insights into interface roles and pairing mechanisms from STM, ARPES, and transport studies

Abstract

Cuprate high temperature superconductors consist of two quasi-two-dimensional (2D) substructures: CuO2 superconducting layers and charge reservoir layers. The superconductivity is realized by charge transfer from the charge reservoir layers into the superconducting layers without chemical dopants and defects being introduced into the latter, similar to modulation-doping in semiconductor superlattices of AlGaAs/GaAs. Inspired by this scheme, we have been searching for high temperature superconductivity in ultrathin films of superconductors epitaxially grown on semiconductor/oxide substrates since 2008. We have observed interface enhanced superconductivity in both conventional and unconventional superconducting films, including single atomic layer films of Pb and In on Si substrates and single unit cell (UC) films of FeSe on SrTiO3 (STO) substrates. The discovery of high temperature superconductivity with a superconducting gap of ~20 meV in 1UC-FeSe/STO has stimulated tremendous interest in superconductivity community, for it opens new avenue for both raising superconducting transition temperature and understanding the pairing mechanism of unconventional high temperature superconductivity. Here, we review mainly the experimental progress on interface enhanced superconductivity in the three systems mentioned above with emphasis on 1UC-FeSe/STO, studied by scanning tunneling microscopy/spectroscopy, angle-resolved photoemission spectroscopy and transport experiments. We discuss the roles of interfaces and possible pairing mechanism inferred from those studies.