Superconductivity in a Scandium Borocarbide with a Layered Crystal Structure

TL;DR

This paper reports the discovery of superconductivity at 7.7 K in a newly synthesized scandium borocarbide compound with a layered tetragonal structure, highlighting the role of boron and scandium orbitals in its superconducting properties.

Contribution

It introduces a new ternary scandium borocarbide with a specific layered structure and demonstrates its superconductivity, combining experimental structure determination and theoretical electronic analysis.

Findings

Superconductivity observed at 7.7 K in the new compound

Boron is essential for structural stability

Sc-3d orbitals mainly contribute to superconductivity

Abstract

The discovery of nearly room-temperature superconductivity in superhydrides has motivated further materials research for conventional superconductors. To realize the moderately high critical temperature $(T_\mathrm{c})$ in materials containing light elements, we explored new superconducting phases in a scandium borocarbide system. Here, we report the observation of superconductivity in a new ternary Sc-B-C compound. The crystal structure, which was determined through a Rietveld analysis, belongs to tetragonal space group $P4/ncc$. By complementarily using the density functional theory calculations, a chemical formula of the compound was found to be expressed as Sc$_{20}$C$_{8-x}$B$_x$C$_{20}$($x=1\:\mathrm{or}\:2$). Interestingly, a small amount of B is essential to stabilize the present structure. Our experiments revealed the typical type-II superconductivity at $T_\mathrm{c}=7.7\:\mathrm{K}$. Additionally, we calculated the density of states within a first-principles approach and found that the contribution of the Sc-3d orbital was mainly responsible for the superconductivity.