Interface superconductivity in FeSe thin films on SrTiO$_3$grown by the PLD technique

TL;DR

This study demonstrates that FeSe thin films grown on SrTiO$_3$ using pulsed laser deposition exhibit high-temperature interface superconductivity without post-annealing, offering a versatile method for exploring and enhancing superconductivity at interfaces.

Contribution

First demonstration of interface superconductivity in FeSe/STO films grown by PLD without post-annealing, enabling systematic interface engineering for higher $T_{ m c}$.

Findings

Superconductivity with high $T_{ m c}$ observed in PLD-grown FeSe/STO films.

$T_{ m c}$ increases as film thickness decreases, consistent with MBE results.

PLD technique allows easy fabrication of various interfaces for studying interface superconductivity.

Abstract

In this study, we fabricate 5-30-nm-thick films of FeSe/STO using pulsed laser deposition (PLD). The grown films exhibit superconductivity with an onset $T_{\mathrm{c}}$ that is much higher than that of bulk FeSe under ambient pressure. The observed $T_{\mathrm{c}}$ values are exceptionally high in terms of the strain vs. $T_{\mathrm{c}}$ relationship of the same material established so far. Furthermore, $T_{\mathrm{c}}$ increases as the film thickness decreases, except for films thinner than 10 nm. This thickness dependence of $T_{\mathrm{c}}$ is in good agreement with the results reported for films grown by molecular beam epitaxy (MBE) that exhibit interface superconductivity. These results indicate the realization of interface superconductivity in PLD-grown FeSe/STO. Furthermore, our PLD technique requires no post-annealing to realize interface superconductivity, which is different from MBE techniques. Because the PLD technique has the advantage that various interfaces can be fabricated easily by simply altering the target materials, our results open novel routes to study interface superconductivity toward higher $T_{\mathrm{c}}$ by systematic control of the interface.