Systematic study of two-band/two-gap superconductivity in carbon-substituted MgB2 by point-contact spectroscopy -: art. no. 064520

Point-contact measurements on the carbon-substituted Mg(B1-xCx)(2) filament/powder samples directly reveal a retention of the two superconducting energy gaps in the whole doping range from x=0 to xapproximate to0.1. The large gap on the sigma-band is decreased in an essentially linear fashion with increasing the carbon concentrations. The changes in the small gap Delta(pi) up to 3.8% C are proportionally smaller and are more difficult to detect but for the heavily doped sample with xapproximate to0.1 and T-c=22 K both gaps are still present, and significantly reduced, consistent with a strong essentially linear, reduction of each gap with the transition temperature.