Anomalous anisotropy of deuterium-grown boron-doped diamond and the role of boron-tetramers in the Mott-Insulator transition

We show anisotropy in the superconductivity for boron-doped diamond thin films prepared with Microwave Plasma Assisted Chemical Vapor Deposition using deuterium-rich plasma. This anomalous phase transition is linked with the emergence of boson quantum entanglement states behaving as a bosonic insulating state. Here, we show that the superconducting properties of the diamond film are anisotropic, which might enable applications such as single-photon detectors. This formation of a dirty superconductivity state is related to the type of boron dimers formed as well as the crystallographic orientation of the crystallites. We use quantum mechanics to determine the states formed by B dopants. We find that isolated B sites prefer to form BB dimers and that a pair of dimers prefer to aggregate to form the BBCBB cluster oriented along a <110> direction. We find that this BBCBB defect leads to metallic character with holes in the valence band near the G point and electrons in a BBCBB promoted band at the K point. Thus the BBCBB defect is responsible for the Mott Insulator Transition and presumably the superconductivity.