Experimental indications of a BCS behaviour in superconducting diamond

We present a scanning tunneling spectroscopy study of a superconducting single-crystalline heavily boron-doped diamond which provides an experimental evidence for BCS behaviour. The superconducting gap, its temperature dependence, its relationship to the bulk critical temperature as well as the shape of the tunneling density of states are found to be fully compatible with a conventional BCS-type weak-coupling mechanism. A Raman backscattering spectroscopy study of diamond epilayers with different doping levels indicates by a slight phonon softening a coupling between carriers and optical phonons. In addition, in the mixed state, the disordered Abrikosov lattice of vortices were imaged using STM spectroscopy. Localized states at energies strikingly much higher than expected for low-lying quasiparticles excitations appear in the tunneling density of states of the vortex core. (copyright 2006 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)