Magnetic Field Dependence of the Low-Temperature Specific Heat of the Borocarbide Superconductor LuNi2B2C

Abstract

The low temperature specific heat of the borocarbide superconductor LuNi 2 B 2 C was measured under various magnetic fields ( H ) up to 8 T. The coefficient of the T -linear term in specific heat in the mixed state shows marked deviations from the H -linear dependence expected for conventional superconductors and is found to obey a \(\sqrt{H}\) dependence. A good description of the data can be obtained by assuming the presence of a zero-gap region along lines on the Fermi surface, indicating the possibility of unconventional pairing in the superconducting state of the borocarbides.