LA2-XSRXCUO4 - LOW-TEMPERATURE SPECIFIC-HEAT AND THERMAL-CONDUCTIVITY

We present simultaneous measurements of the low temperature (0.04K to 1.2K) specific heat and thermal conductivity for a series of four sintered samples from the La2-xSrxCuO4 system. By systematically varying the strontium (hole) concentration from x = 0.05 (near-insulator) through to x = 0.27 (near-metallic), we were able to study the thermal properties of the different superconducting regimes in this cuprate system. The thermal conductivity data are characterised by a weakening of the temperature dependence from T almost-equal-to 3 to T almost-equal-to 1, observed in all the samples below 1K. A linear temperature variation in the specific heat data for the two most inhomogeneous superconductors (x = 0.05 and 0.27) was replaced by a T0.5 dependence for the samples with the higher transition temperatures (x = 0.1 and 0.15). The specific heats of all the samples showed a large upturn (proportional to T-2) at the lowest temperatures. The coefficients of this T-2 term were found to have a minimum for x = 0.15. We discuss these effects in terms of possible transport mechanisms.