Title: Compressed H$_3$S: inter-sublattice Coulomb coupling in a high-$\textit{T}$$_C$ superconductor,
Abstract: Upon thermal annealing at or above room temperature (RT) and high pressure
$\it P$ $\sim$ 155 GPa, H$_3$S exhibits superconductivity at $\it T_C$ $\sim$
200 K. Various theoretical frameworks with strong electron-phonon coupling and
Coulomb repulsion have reproduced this record-level $\it T_C$. Of particular
relevance is that observed H-D isotopic correlations among $\it T_C$, $\it P$,
and annealed order indicate limitations on the H-D isotope effect, leaving open
for consideration unconventional high-$\it T_C$ superconductivity with
electronic-based enhancements. The present work examines Coulombic pairing
arising from interactions between neighboring S and H species on separate
interlaced sublattices constituting H$_3$S in the Im$\overline{3}$m structure.
The optimal transition temperature is calculated from $\it{T}$$_{C0}$ =
$\it{k}$$_B$$^{-1}$$\Lambda$$\it{e}$$^2$/$\ell$$\zeta$, with $\Lambda$ =
0.007465 $\AA$, inter-sublattice S-H separation spacing $\zeta$ =
$\it{a}$$_0$/$\sqrt{2}$, interaction charge linear spacing $\ell$ =
$\it{a}$$_0$(3/$\sigma$)$^{1/2}$, average participating charge fraction
$\sigma$ = 3.43 $\pm$ 0.10 estimated from theory, and lattice parameter
$\it{a}$$_0$ = 3.0823 \AA. The result $\it{T}$$_{C0}$ = 198.5 $\pm$ 3.0 K is in
excellent agreement with transition temperatures determined from resistivity
and susceptibility data. Analysis of mid-infrared reflectivity confirms
correlation between boson energy and $\zeta$$^{-1}$. Suppression of $\it T_C$
with increasing residual resistance for $<$ RT annealing is treated by
scattering-induced pair breaking. Correspondence with layered high-$\it T_C$
superconductor structures are discussed. A model considering Compton scattering
of virtual photons of energies $\leq$ $\it e$$^2$/$\zeta$ by inter-sublattice
electrons is introduced, illustrating $\Lambda$ is proportional to the reduced
electron Compton wavelength.