科研之友
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摘要
Upon thermal annealing at or above room temperature (RT) and at high hydrostatic pressure P similar to 155 GPa, sulfur trihydride H3S exhibits a measured maximum superconducting transition temperature T-c similar to 200K. 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 a 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 Im (3) over barm structure, The optimal value of the transition temperature is calculated from T-co = k(B)(-1) Lambda e(2)1l zeta, with Lambda = 0.007465 angstrom, inter-sublattice S-H separation spacing zeta= aol-\/2, interaction charge linear spacing L= a, (3/sigma)112, average participating charge fraction sigma = 3.43 +/- 0.10 estimated from calculated It-projected electron states, and lattice parameter a(0) = 3,0823 A at P = 155 GPa. The resulting value of To) = 198.5 +/- 3.0K is in excellent agreement with transition temperatures determined from resistivity (196-200K onsets, 190-197K midpoints), susceptibility (200K onset), and critical magnetic acids (203,5 K by extrapolation), Analysis of mid-infrared reflectivity data confirms the expected correlation between boson energy and zeta(-1), Suppression of Tc below T-co, correlating with increasing residual resistance for < RT annealing, is treated in terms of scattering-induced pair breaking, Correspondences between H3S and layered high-Tc superconductor structures are also discussed, and a model considering Compton scattering of
- 出版日期2017-11-8
