Growth of Single Unit-Cell Superconducting La$_{2-x}$Sr$_x$CuO$_{4}$ Films

TL;DR

This paper reports a new molecular beam epitaxy method to grow high-quality single-unit-cell La$_{2-x}$Sr$_x$CuO$_{4}$ superconducting films with a transition temperature of 12.5 K, advancing ultrathin film fabrication.

Contribution

Introduces a homoepitaxial buffer layer technique to produce ultrathin La$_{2-x}$Sr$_x$CuO$_{4}$ films with minimal interface degradation, enabling superconductivity in a single unit cell.

Findings

Superconductivity observed in a single unit-cell film at 12.5 K

Achieved minimal film thickness for superconductivity

Measured in-plane magnetic penetration depth of 535 nm

Abstract

We have developed an approach to grow high quality ultrathin films of La$_{2-x}$Sr$_x$CuO$_{4}$ with molecular beam epitaxy, by adding a homoepitaxial buffer layer in order to minimize the degradation of the film structure at the interface. The advantage of this method is to enable a further reduction of the minimal thickness of a superconducting La$_{1.9}$Sr$_{0.1}$CuO$_{4}$ film. The main result of our work is that a single unit cell (only two copper oxide planes) grown on a SrLaAlO$_4$ substrate exhibits a superconducting transition at 12.5 K (zero resistance) and an in-plane magnetic penetration depth $\lambda_{ab}(0)$ = 535 nm.