Superconductivity in orthorhombic NbS

作者：Bin-Bin Ruan, Junkun Yi, Le-Wei Chen, Menghu Zhou, Yun-Qing Shi, Qingsong Yang, Yadong Gu, Genfu Chen, Zhi-An Ren · 发表于：Physical review. B./Physical review. B · 年份：2023 · DOI：10.1103/physrevb.108.174517 · 被引用次数：9 · 研究领域：2D Materials and Applications、Iron-based superconductors research、MXene and MAX Phase Materials

Compared to the intensively studied niobium dichalcogenides, the physical properties of niobium monosulfide (NbS) have been less explored. Here we report the discovery of bulk superconductivity in orthorhombic NbS ($o$-NbS). First-principles results of $o$-NbS are also revealed. $o$-NbS crystallizes in a MnP-type structure ($Pnma$) with lattice parameters $a=\text{6.4450(1)}$ \AA{}, $b=\text{3.3 1770(4)}$ \AA{}, and $c=\text{5.8629(1)}$ \AA{}. It exhibits type-II superconductivity with a critical temperature (${T}_{\mathrm{c}}$) of 6.0 K. Bulk superconductivity is confirmed by the magnetization and heat capacity measurements. The upper and lower critical fields are 7.4 T and 13.0 mT, respectively. Specific heat data suggest that $o$-NbS is a fully gapped $s$-wave superconductor, with ${\mathrm{\ensuremath{\Delta}}}_{0}/{k}_{\mathrm{B}}{T}_{\mathrm{c}}=1.75$ and $\mathrm{\ensuremath{\Delta}}{C}_{\mathrm{e}}/\ensuremath{\gamma}{T}_{\mathrm{c}}=1.45$, fitting perfectly within the BCS theory. First-principles calculations indicate that the $\mathrm{Nb}\text{\ensuremath{-}}4d$ states dominate the Fermi level (${E}_{\mathrm{F}}$), and the density of states (DOS) on ${E}_{\mathrm{F}}$ is sensitive to niobium vacancies. Different from the quasi-two-dimensional $2H\text{\ensuremath{-}}{\mathrm{NbS}}_{2}$ and quasi-one-dimensional ${\mathrm{Nb}}_{3}{\mathrm{S}}_{4}$ superconductors, our discovery of superconductivity in three-dimensional $o$-NbS provides a different motif for both expe...