LOW-TEMPERATURE ELECTRONIC SPECIFIC-HEAT OF LA2-XSRXCUO4 AND LA2-XSRXCU1-YZNYO(4)

The electronic specific heat C-e1 was studied at T less than or equal to 10 K both on La2-xSrxCuO4 samples and on La2-xSrxCu1-yZnyO4 samples below and above y(c) at which the superconductivity disappears. In su perconducting La2-xSrxCuO4 samples, the C-e1 contains only a T-2 compo nent at T << T-c in a x range between 0.14 and 0.22, suggesting a gapl ess superconductor with line nodes. A T linear component of C-e1 appea rs in superconducting La2-xSrxCu1-yZnyO4 (y<y(c)) samples, and its coe fficient, y, increases markedly with Zn content. In samples with vario us Zn contents, the relation between T-c/T-c(y=0) and y/y(y greater th an or equal to y(c)) can be understood in terms of strong impurity sca ttering in a d wave superconductor.