Hole superconductivity in H2SH2S and other sulfides under high pressure

• An explanation for the high Tc observed in hydrogen sulfide is proposed.
• High pressure leads to overlap of p-orbitals of neighboring S=anions.
• Holes conduct in a planar structure of S=anions.
• Pairing of holes is driven by the mechanism of hole superconductivity.
• Electron–phonon interaction plays no role in the superconductivity.

Superconductivity at temperatures up to 190 K at high pressures has recently been observed in H2SH2S and interpreted as conventional BCS-electron–phonon-driven superconductivity (Drozdov et al., 2014). Instead we propose that it is another example of the mechanism of hole superconductivity at work. Within this mechanism high temperature superconductivity arises when holes conduct through negatively charged anions in close proximity. We propose that electron transfer from H to S leads to conduction by holes in a nearly full band arising from direct overlap of S=S=p   orbitals in a planar structure. The superconductivity is non-phononic and is driven by pairing of heavily dressed hole carriers to lower their kinetic energy. Possible explanations for the observed lower critical temperature of D2SD2S are discussed. We predict that high temperature superconductivity will also be found in other sulfides under high pressure such as Li2S,Na2S and K2SK2S.