High-temperature surface superconductivity in rhombohedral graphite

N. B. Kopnin; M. Ijäs; A. Harju; T. T. Heikkilä

doi:10.1103/PhysRevB.87.140503

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High-temperature surface superconductivity in rhombohedral graphite

N. B. Kopnin, M. Ijäs, A. Harju, T. T. Heikkilä

DOI 10.1103/PhysRevB.87.140503 · Physical Review B

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Abstract

Surface superconductivity in rhombohedral graphite is a robust phenomenon which can exist even when higher order hoppings between the layers lift the topological protection of the surface flat band and introduce a quadratic dispersion of electrons with a heavy effective mass. We show that for weak pairing interaction, the flat-band character of the surface superconductivity transforms into a BCS-like relation with high critical temperature characterized by a higher coupling constant due to a much larger density of states than in the bulk. Our results offer an explanation for the recent findings of graphite superconductivity with an unusually high transition temperature.