Abstract
The low-temperature heat capacity of single crystals of κ-(BEDT-TTF)2Cu[N(CN)2]Br was studied by the thermal relaxation technique in the temperature range between 0.11K and 4.2K. By analyzing temperature dependence data of electronic heat capacity Cel, we can see a quadratic term due to the quasiparticle excitations over the superconductive gap exists at low-temperature region below 2K. The recovery rate of electronic heat capacity coefficient γ is found to obey square root of external magnetic fields H. These results demonstrate that the superconductivity of this material is an unconventional one with line-nodes in the superconductive gap.
