Existence of the Minimum Coefficient in Temperature Linear Term of Heat Capacity in Superconducting (La_1−xBa_x)₂CuO₄

Abstract

In high-T_c superconductors (La_1−xM_x)₂CuO₄ (M=Ba, Sr), it has been reported that the heat capacity has a nonzero coefficient γ in the temperature linear term. We investigated the detailed dependence of γ on Ba doping. It was confirmed that γ becomes zero for undoped La₂CuO₄. With increasing Ba concentration x, γ increases markedly up to x=0.02 where the magnetic order almost disappears, while it decreases as superconductivity starts to appear and then has a minimum around x=0.04. With further increasing x, γ increases again. These results may be due to a combined effect of two different contributions to γ.