Metal-insulator transition and superconductivity in boron-doped diamond

• We report on a detailed analysis of the transport properties and superconducting critical temperatures of boron-doped diamond films grown along the {100} direction. The system presents a metal-insulator transition (MIT) for a boron concentration (nB) on the order of nc~4.5×1020  cm−3, in excellent agreement with numerical calculations. The temperature dependence of the conductivity and Hall effect can be well described by variable range hopping for nB<nc with a characteristic hopping temperature T0 strongly reduced due to the proximity of the MIT. All metallic samples (i.e., for nB>nc) present a superconducting transition at low temperature. The zero-temperature conductivity 0 deduced from fits to the data above the critical temperature (Tc) using a classical quantum interference formula scales as 0(nB/nc−1) with ~1. Large Tc values (0.4  K) have been obtained for boron concentration down to nB/nc~1.1 and Tc surprisingly mimics a (nB/nc−1)1/2 law. Those high Tc values can be explained by a slow decrease of the electron-phonon coupling parameter and a corresponding drop of the Coulomb pseudopotential µ* as nBnc.

Ämnesord

NATURVETENSKAP  -- Fysik (hsv//swe)

NATURAL SCIENCES  -- Physical Sciences (hsv//eng)

Nyckelord

diamond

superconducting materials

boron

metal-insulator transition

Hall effect

hopping conduction

superconducting transitions

superconducting transition temperature

electron-phonon interactions

superconducting thin films

NATURAL SCIENCES

NATURVETENSKAP

Physics

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