Superconducting and normal state properties of heavily hole-doped diamond synthesized at high pressure

Abstract

Diamonds, synthesized at high pressures and high temperatures in the presence of boron, are heavily hole-doped by incorporation of boron into the diamond lattice. These diamonds become superconducting below T c ¼ 2-9 K. Synthesis in the systems B-C and B 4 C-C at P ¼ 9 GPa and T ¼ 2500-2800 K result in formation of polycrystalline carbonado-like material, whereas synthesis from B-C-H gives small single crystals and intergrowth plates. Dense superconducting bodies can be prepared by compacting these single crystal particles at P ¼ 8 GPa and T ¼ 1800 K. Specific heat and resistivity measurements in magnetic fields prove the bulk nature of superconductivity in all pressure-synthesized samples and provide a consistent set of materials parameters that favor a conventional weak-coupling electron-phonon interpretation of the superconducting mechanism at high hole doping. Schottky barrier tunneling conductance spectra, obtained with contacts fabricated at the surface of these hole-doped diamonds, indicate the appearance of superconducting gap below T c .

Superconductivity in compensated and uncompensated semiconductors

“…This means that the long-range correlation is enhanced by increasing the concentration of impurities. This is consistent with the experimental observation that the T c of B-doped diamond increases with increasing the boron concentration [21,22,32,43]. Note that the impurity concentration n imp in our definition corresponds to the concentration of isolated substitutional boron acceptors.…”

“…Experimental studies have examined which scenario describes better the electronic structure of B-doped diamond [30][31][32][33][34][35][36][37]. We point out here that the two scenarios are not contradictory and can be described continuously.…”

11B nuclear magnetic resonance in boron-doped diamond

“…Detailed studies have been reported on synthesis and characterization of heavily boron-doped diamond [5][6][7][8][9]. Despite the gained insights, the relation between the local structure around boron dopants and physical properties of boron-doped diamond has not been fully clarified.…”