Suppression of superconductivity in FeSe films under tensile strain

TL;DR

This study investigates how tensile strain affects superconductivity in FeSe films, finding that tensile strain suppresses superconductivity, unlike unstrained films which exhibit superconducting transitions near 8 K.

Contribution

It provides experimental evidence that tensile strain suppresses superconductivity in FeSe films, highlighting the importance of strain management in superconductor fabrication.

Findings

Superconductivity observed in unstrained FeSe films at ~8 K.

Tensile strain suppresses superconductivity down to 5 K.

Tensile strain effects depend on substrate and film thickness.

Abstract

We have studied the effect of tensile strain on the superconductivity in FeSe films. 50 nm, 100 nm, and 200 nm FeSe films were grown on MgO, SrTiO$_3$, and LaAlO$_3$ substrates by using a pulsed laser deposition technique. X-ray diffraction analysis showed that the tetragonal phase is dominant in all of our FeSe films. The 50 nm FeSe films on MgO and SrTiO$_3$ are under tensile strain, while the 50 nm FeSe film on LaAlO$_3$ and the other thick FeSe films are unstrained. Superconducting transitions have been observed in unstrained FeSe films with T$_{onset}$ $\approx$ 8 K, which is close to the bulk value. However, no sign of superconductivity has been observed in FeSe films under tensile strain down to 5 K. There is evidence to show that tensile strain suppresses superconductivity in FeSe films.