Superconductivity in orthorhombic NbS

Bin-Bin Ruan; Jun-Kun Yi; Le-Wei Chen; Menghu Zhou; Yun-Qing Shi; Qing-Song Yang; Ya-Dong Gu; Gen-Fu Chen; Zhi-An Ren

doi:10.1103/PhysRevB.108.174517

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Superconductivity in orthorhombic NbS

Bin-Bin Ruan, Jun-Kun Yi, Le-Wei Chen, Menghu Zhou, Yun-Qing Shi, Qing-Song Yang, Ya-Dong Gu, Gen-Fu Chen, Zhi-An Ren

DOI 10.1103/PhysRevB.108.174517 · Physical Review B

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Abstract

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=6.4450(1) Å, b=3.3 1770(4) Å, and c=5.8629(1) Å. It exhibits type-II superconductivity with a critical temperature (Tc) 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 Δ0/kBTc=1.75 and ΔCe/γTc=1.45, fitting perfectly within the BCS theory. First-principles calculations indicate that the Nb−4d states dominate the Fermi level (EF), and the density of states (DOS) on EF is sensitive to niobium vacancies. Different from the quasi-two-dimensional 2H−NbS2 and quasi-one-dimensional Nb3S4 superconductors, our discovery of superconductivity in three-dimensional o-NbS provides a different motif for both experimental and theoretical studies.

Source-reported materials — not catalogue approval

Formula	Reported Tc (K)	Pressure (GPa)	Type
NbS Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	6	Pressure not reported	onset
NbS Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	5.5	Pressure not reported	midpoint
NbS Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	5.2	Pressure not reported	zero_resistance
NbS Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	4.8	Pressure not reported	unknown
NbS Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	5.1	Pressure not reported	unknown
NbS2 Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	6.2	Pressure not reported	unknown
Nb3S4 Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	4	Pressure not reported	unknown
Nb21S8 Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	4.1	Pressure not reported	unknown