Soft X-ray angle-resolved photoemission spectroscopy of heavily boron-doped superconducting diamond films

We report on an investigation of superconductivity in n-type InN. There is an optimum carrier density for the occurrence of the superconductivity. The lowest carrier density is limited by the Mott transition of ne~ 2 1017 cm 3 and the highest density is limited by the superconductor to insulator transition of ne~ 5 1020 cm 3. We propose a mechanism where the occurrence of the superconductivity is related to the presence of In–In chains of finite length in the ab plane. The In–In chains, which originate from the inversion domains of InN grown on sapphire (0 0 0 1) and elongate along , are coupled toform micro Josephson-junctions.