Role of hydrogen in the electronic properties of CaFeAsH-based superconductors
Y. N. Huang, D. Y. Liu, L. J. Zou, W. E. Pickett
DOI 10.1103/PhysRevB.93.195148 · Physical Review B
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Abstract
The electronic and magnetic properties of the hydride superconductor CaFeAsH, which superconducts up to 47 K when electron doped with La, and the isovalent alloy system CaFeAsH1−xFx are investigated using density functional based methods. The Q⃗=(π,π,0) peak of the nesting function ξ(q⃗) is found to be extremely strong and sharp, and the additional structure in ξ(q⃗) associated with the near-circular Fermi surfaces (FSs) that may impact low energy excitations is quantified. The unusual band introduced by H, which shows strong dispersion perpendicular to the FeAs layers, is shown to be connected to a peculiar van Hove singularity just below the Fermi level. This band provides a three-dimensional electron ellipsoid Fermi surface not present in other Fe-based superconducting materials nor in CaFeAsF. Electron doping by 25% La or Co has a minor effect on this ellipsoid Fermi surface, but suppresses FS nesting strongly, consistent with the viewpoint that eliminating strong nesting and the associated magnetic order allows high Tc superconductivity to emerge. Various aspects of the isovalent alloy system CaFeAsH1−xFx and means of electron doping are discussed in terms of influence of incipient bands.
Source-reported materials — not catalogue approval
| Formula | Reported Tc (K) | Pressure (GPa) | Type |
|---|---|---|---|
| CaFeAsH Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula. | 25 | 3 GPa | onset |
| CaFeAsF Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula. | 25 | 3 GPa | onset |
| Ca0.75La0.25FeAsH Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula. | 47 | Pressure not reported | unknown |
| CaFe0.75Co0.25AsH Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula. | 23 | Pressure not reported | unknown |
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