Superconductivity in monolayer Ba$_2$N electride: a first-principles study

TL;DR

This study uses first-principles calculations to investigate the electronic and superconducting properties of monolayer Ba$_2$N electride, revealing strain-enhanced superconductivity with potential implications for other electride materials.

Contribution

It provides the first detailed theoretical analysis of superconductivity in monolayer Ba$_2$N electride, highlighting strain effects on $T_c$ and electron-phonon interactions.

Findings

Monolayer Ba$_2$N has a low work function of 3.0 eV.

Predicted superconducting transition temperature ($T_c$) is 3.4 K.

Tensile strain increases $T_c$, reaching 10.8 K at 4% strain.

Abstract

The exploration of superconductivity in low-dimensional materials has attracted intensive attention for decades. Based on first-principles electronic structure calculations, we have systematically investigated the electronic and superconducting properties of the two-dimensional electride Ba$_2$N in the monolayer limit. Our results show that monolayer Ba$_2$N has a low work function of 3.0 eV and a predicted superconducting transition temperature ($T_c$) of 3.4 K. The superconductivity can be further improved with the tensile strain, which results from the increase of density of states at the Fermi level as well as the enhanced coupling between inner-layer electrons and phonons. Remarkably, at the 4$\%$ tensile strain, the acoustic branches have noticeable softening at the K point of Brillouin zone and the superconducting $T_c$ can reach 10.8 K. The effect of lattice strain on the electron transfer from the superficial region to the inner-layer region of monolayer Ba$_2$N may also apply to other electride materials and influence their physical properties.