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

摘要

A first-principles investigation of the electron-phonon interaction in therecently synthesized osmium dinitride (OsN$_2$) compound predicts that thematerial is a superconductor. Superconductivity in OsN$_2$ would originate fromthe stretching of covalently bonded dinitrogen units embedded in thetransition-metal matrix, thus adding dinitrides to the class of superconductorscontaining covalently bonded light elements. The dinitrogen vibrations arestrongly coupled to the electronic states at the Fermi level and generatenarrow peaks in the Eliashberg spectral function $\alpha^2F(\omega)$. The totalelectron-phonon coupling of OsN$_2$ is $\lambda=0.37$ and the estimatedsuperconducting temperature T$_c \approx 1$ K. We suggest that thesuperconducting temperature can be substantially increased by hole doping ofthe pristine compound and show that T$_c$ increases to 4 K with a dopingconcentration of 0.25 holes/OsN$_2$ unit.