Anomalous thermal conductivity of La2-xSrxCuO4: Possibility of a polaronic glass

Abstract

We present measurements of the thermal conductivity of La2CuO4 and La1.85Sr0.15CuO4. The results on the pure sample show that lattice conduction is predominant with a T1.8 dependence at low temperatures and a strong T-independent scattering above 30 K. We observe a similar behavior for the superconductor but with a T1.4 law at low temperature and a small electronic contribution in the normal state. These results together with the behavior of the specific heat and sound attenuation are consistent with the existence of a two-level tunneling system for an amorphous state.