First-principles study of the superconductivity in LaO

TL;DR

This study uses first-principles calculations to analyze the superconductivity mechanism in LaO, revealing it is conventional BCS type and can be enhanced by strain and doping, with potential for higher $T_c$ in thin films.

Contribution

It provides the first theoretical elucidation of LaO's superconductivity mechanism and explores how strain and doping can enhance its critical temperature.

Findings

Superconductivity in LaO is of the conventional BCS type.

Electron doping and tensile strain can significantly increase $T_c$.

Superconductivity persists in LaO thin films down to trilayer thickness.

Abstract

A recent experiment reported the first rare-earth binary oxide superconductor LaO ($T_c $ $\sim$ 5 K) with a rock-salt structure [K. Kaminaga et al., J. Am. Chem. Soc. 140, 6754 (2018)]. Correspondingly, the underlying superconducting mechanism in LaO needs theoretical elucidation. Based on first-principles calculations on the electronic structure, lattice dynamics, and electron-phonon coupling of LaO, we show that the superconducting pairing in LaO belongs to the conventional Bardeen-Cooper-Schrieffer (BCS) type. Remarkably, the electrons and phonons of the heavy La atoms, instead of those of the light O atoms, contribute most to the electron-phonon coupling. We further find that both the biaxial tensile strain and the pure electron doping can enhance the superconducting $T_c$ of LaO. With the synergistic effect of electron doping and tensile strain, the $T_c$ could be even higher, for example, 11.11 K at a doping of 0.2 electrons per formula unit and a tensile strain of $4\%$. Moreover, our calculations show that the superconductivity in LaO thin film remains down to the trilayer thickness with a $T_c$ of 1.4 K.