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- Title
Modeling Intercalated Group-4-Metal Nitride Halide Superconductivity with Interlayer Coulomb Coupling.
- Authors
Harshman, Dale; Fiory, Anthony
- Abstract
Behavior consistent with Coulomb-mediated high- T superconductivity is shown to be present in the intercalated group-4-metal nitride halides A( S) MN X, where the MN X host ( M = Ti, Zr, Hf; X = Cl, Br) is partially intercalated with cations A and optionally molecular species ( S) in the van der Waals gap between the halide X layers, expanding the basal-plane spacing d. The optimal transition temperature is modeled by T ∝ ζ( σ/ A), where the participating fractional charge per area per formula unit σ/ A and the distance ζ, given by the transverse A- X separation ( ζ < d), govern the interlayer Coulomb coupling. From experiment results for β-form compounds based on Zr and Hf, in which concentrations x of A are varied, it is shown that σ = γ[ v( x − x)], where x is the optimal doping, x is the onset of superconducting behavior, v is the A charge state, and γ = 1/8 is a factor determined by the model. Observations of T < T in the comparatively more disordered α- A( S)TiN X compounds are modeled as pair breaking by remote Coulomb scattering from the A cations, which attenuates exponentially with increasing ζ. The T values calculated for nine A( S) MNCl compounds, shown to be optimal, agree with the measured T to within experimental error. The model for T is also found to be consistent with the absence of high- T characteristics for A MN X compounds in which a spatially separated intercalation layer is not formed.
- Subjects
TITANIUM nitride; ZIRCONIUM chlorides; SUPERCONDUCTIVITY; COULOMB functions; HAFNIUM tetrachloride; TRANSITION temperature; VAN der Waals forces
- Publication
Journal of Superconductivity & Novel Magnetism, 2015, Vol 28, Issue 10, p2967
- ISSN
1557-1939
- Publication type
Article
- DOI
10.1007/s10948-015-3147-x