Boron-doped diamond — Grained Mott's metal revealing superconductivity

Reconsidering the experimental data on superconducting transition in heavily boron-doped polycrystalline diamond films, we have suggested an original theoretical model based on the concept of disordered Mott's metal in which the transport above TC is controlled by weak localization of holes. It has been shown that in the Kelvin temperature range the spins of holes occupying the neighboring weakly localized orbits must be strongly correlated and that just this effect, which is fully analogous to the Cooper pairing known in classical superconductors, can account for the existence of superconductivity transition in this material. The possible influence of grain boundaries on the superconducting transition is discussed in the framework of a simple model. Assuming thermal noise as a source voltage difference between adjacent grains, a phase diagram determining the region of stability of superconducting state depending on grain size is derived.