First-principles study of the superconductivity in LaO

A recent experiment reported the first rare-earth binary oxide superconductor LaO (T-c similar to 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.

Automated summary

The study found that the superconducting pairing in LaO belongs to the BCS type, with the heavy La atoms' electrons and phonons playing a major role in electron-phonon coupling. Biaxial tensile strain and pure electron doping can enhance the superconducting Tc of LaO, and with synergistic effect, Tc can be even higher. Additionally, superconductivity in LaO thin film remains down to the trilayer thickness with a Tc of 1.4 K.