Room temperature superconductivity dome at a Fano resonance in superlattices of wires

Abstract

Recently room temperature superconductivity with Tc=15 degrees Celsius has been discovered in a pressurized complex ternary hydride, CSHx, which is a carbon doped H3S alloy. The nanoscale structure of H3S is a particular realization of the 1993 patent claim of superlattice of quantum wires for room temperature superconductors where the maximum Tc occurs at the top of a superconducting dome. Here we focus on the electronic structure of materials showing nanoscale heterostructures at atomic limit made of a superlattice of quantum wires like hole doped cuprate perovskites, organics, A15 intermetallics and pressurized hydrides. We provide a perspective of the theory of room temperature multigap superconductivity in heterogeneous materials tuned at a Fano Feshbach resonance (called also shape resonance) in the superconducting gaps focusing on H3S where the maximum Tc occurs where the pressure tunes the chemical pressure near a topological Lifshitz transition. Here the superconductivity dome of Tc versus pressure is driven by both electron-phonon coupling and contact exchange interaction. We show that the Tc amplification up to room temperature is driven by the Fano Feshbach resonance between a superconducting gap in the anti-adiabatic regime and other gaps in the adiabatic regime. In these cases the Tc amplification via contact exchange interaction is the missing term in conventional multiband BCS and anisotropic Migdal-Eliashberg theories including only Cooper pairing