**Theory of high- T_{C} Superconductivity: Transition temperature**, D. R. Harshman, A. T. Fiory and J. D. Dow [arXiv]

It is demonstrated that the transition temperature (*T*_{C}) of high-*T*_{C} superconductors is determined by their layered crystal structure, bond lengths, valency properties of the ions, and Coulomb coupling between electronic bands in adjacent, spatially separated layers. Analysis of 31 high-*T*_{C} materials (cuprates, ruthenates, rutheno-cuprates, iron pnictides, organics) yields the universal relationship for optimal compounds, k_{B}*T*_{C0} = β/ℓζ, where ℓ is related to the mean spacing between interacting charges in the layers, ζ is the distance between interacting electronic layers, β is a universal constant and T_{C0} is the optimal transition temperature (determined to within an uncertainty of ± 1.4 K by this relationship). Non-optimum compounds, in which sample degradation is evident, e.g. by broadened superconducting transitions and diminished Meissner fractions, typically exhibit reduced *T*_{C} < *T*_{C0}. It is shown that *T*_{C0} may be obtained from an average of Coulomb interaction forces between the two layers.

D. R. Harshman, A. T. Fiory and J. D. Dow, J. Phys.: Condens. Matter. **23**, 295701 (2011); Corrigendum, J. Phys.: Condens. Matter **23**, 349501 (2011). This work is also listed in J. Phys.: Condens. Matter Highlights of 2011.