Compressed H3S: Inter-sublattice Coulomb coupling in a high-T C superconductor

Document Type

Article

Publication Date

10-12-2017

Abstract

Upon thermal annealing at or above room temperature (RT) and at high hydrostatic pressure P ∼ 155 GPa, sulfur trihydride H3S exhibits a measured maximum superconducting transition temperature T C ∼ 200 K. Various theoretical frameworks incorporating strong electron-phonon coupling and Coulomb repulsion have reproduced this record-level T C. Of particular relevance is that experimentally observed H-D isotopic correlations among T C, P, and annealed order indicate an H-D isotope effect exponent α limited to values 0.183, leaving open for consideration unconventional high-T C superconductivity with electronic-based enhancements. The work presented herein examines Coulombic pairing arising from interactions between neighboring S and H species on separate interlaced sublattices constituting H3S in the Imm structure. The optimal value of the transition temperature is calculated from T C0 = Λe 2/ ζ, with Λ = 0.007465 Å, inter-sublattice S-H separation spacing ζ = a 0/, interaction charge linear spacing = a 0 (3/σ)1/2, average participating charge fraction σ = 3.43 ± 0.10 estimated from calculated H-projected electron states, and lattice parameter a 0 = 3.0823 Å at P = 155 GPa. The resulting value of T C0 = 198.5 ± 3.0 K is in excellent agreement with transition temperatures determined from resistivity (196-200 K onsets, 190-197 K midpoints), susceptibility (200 K onset), and critical magnetic fields (203.5 K by extrapolation). Analysis of mid-infrared reflectivity data confirms the expected correlation between boson energy and ζ -1. Suppression of T C below T C0, correlating with increasing residual resistance for < RT annealing, is treated in terms of scattering-induced pair breaking. Correspondences between H3S and layered high-T C superconductor structures are also discussed, and a model considering Compton scattering of virtual photons of energies e 2/ζ by inter-sublattice electrons is introduced, illustrating that Λ ∝ C, where C is the reduced electron Compton wavelength.

Identifier

85037706485 (Scopus)

Publication Title

Journal of Physics Condensed Matter

External Full Text Location

https://doi.org/10.1088/1361-648X/aa80d0

e-ISSN

1361648X

ISSN

09538984

PubMed ID

28722689

Issue

44

Volume

29

Fund Ref

University of Notre Dame

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