Experimental constraints on some mechanisms for high-temperature superconductivity

Since its discovery, many mechanisms have been suggested to explain the phenomenon of high-temperature superconductivity in oxides. We propose that experimental data, along with theoretical models, can place constraints on or exclude many of these mechanisms. The isotope shift α, the transition temperature ${\mathit{T}}_{\mathit{c}}$, the ratio of the electronic-specific-heat jump to the normal-state specific heat ΔC/γ${\mathit{T}}_{\mathit{c}}$, and the superconducting gap ratio 2Δ/${\mathit{k}}_{\mathit{B}}$ ${\mathit{T}}_{\mathit{c}}$ are considered. We find limits on the applicability of solely phonon-based and combined phonon-electronic mechanisms.