First-principles investigation of the electron-phonon interaction in OsN$_2$: Theoretical prediction of superconductivity mediated by N-N covalent bonds

TL;DR

This study uses first-principles calculations to predict that OsN₂ is a superconductor with a T_c around 1 K, which can be increased to 4 K through hole doping, highlighting the role of covalent N-N bonds in superconductivity.

Contribution

It provides the first theoretical prediction of superconductivity in OsN₂ mediated by N-N covalent bonds and suggests doping as a way to enhance T_c.

Findings

OsN₂ has a superconducting T_c of approximately 1 K.

Hole doping increases T_c to about 4 K.

Strong coupling between N-N vibrations and electronic states at the Fermi level.

Abstract

A first-principles investigation of the electron-phonon interaction in the recently synthesized osmium dinitride (OsN$_2$) compound predicts that the material is a superconductor. Superconductivity in OsN$_2$ would originate from the stretching of covalently bonded dinitrogen units embedded in the transition-metal matrix, thus adding dinitrides to the class of superconductors containing covalently bonded light elements. The dinitrogen vibrations are strongly coupled to the electronic states at the Fermi level and generate narrow peaks in the Eliashberg spectral function $\alpha^2F(\omega)$. The total electron-phonon coupling of OsN$_2$ is $\lambda=0.37$ and the estimated superconducting temperature T$_c \approx 1$ K. We suggest that the superconducting temperature can be substantially increased by hole doping of the pristine compound and show that T$_c$ increases to 4 K with a doping concentration of 0.25 holes/OsN$_2$ unit.