Influence of a linear term on the density of states of high-Tc superconductors

The temperature dependence of the zero-bias conductance, the electronic specific heat and the ultrasonic attenuation in high-Tc superconductors have been analyzed within the framework of a phenomenological model, based on a density of states expressed as a superposition of a linear term to a BCS standard one. By using the same values of the fitting parameters, we have obtained a satisfactory agreement with the experimental results, together with a consistent physical interpretation of the weight of the linear contribution.