Metal-to-superconductor Transition Induced by Lithium Adsorption on Monolayer 1$T$-Nb$_2$C

TL;DR

This study demonstrates that lithium adsorption on monolayer Nb$_2$C induces a metal-to-superconductor transition with a high critical temperature of 22.1 K, enhanced further by tensile strain, revealing new pathways for high-temperature superconductivity in 2D materials.

Contribution

It is the first computational demonstration of lithium-induced superconductivity in monolayer Nb$_2$C, showing a significant increase in $T_c$ and anisotropic gap distribution, expanding the understanding of functionalization effects.

Findings

Lithium adsorption induces superconductivity with $T_c$ of 22.1 K.

Tensile strain increases $T_c$ to 24 K.

Superconductivity arises from increased electronic states at the Fermi level.

Abstract

Recently, two-dimensional Nb$_2$C has garnered increasing attention due to its functional-group-dependent superconductivity, both experimentally and theoretically. In contrast to the halogen and chalcogen additives that have been the main focus of previous studies, we study the effect of lithium adsorption, which can also be incorporated during the synthesis of Nb$_2$C. Our computational analysis reveals a metal-to-superconductor transition in monolayer Nb$_2$C with a critical temperature ($T_{\mathrm{c}}$) of 22.1 K and a strong anisotropic superconducting gap distribution following the adsorption of lithium atoms. This emergent superconductivity is attributed to the increased electronic states at the Fermi energy, resulting from the contribution of Nb-$d$ orbitals and electron gas states induced by the low electronegativity of lithium. Furthermore, the application of tensile strain raises the $T_{\mathrm{c}}$ to 24 K, which is higher than that of most functional-group-modified Nb$_2$C systems. Our work deepens the understanding of electron-phonon coupling in layered Nb$_2$C, and provides new insights into achieving high critical temperature superconductivity with a strong anisotropic superconducting gap distribution in this system.