Thermal conductivity of superconducting Sr2RuO4 in oriented magnetic fields -: art. no. 064505

We report in-plane thermal conductivity along [100] direction, kappa (100), of high quality single crystals (T-c = 1.44 K) of unconventional superconductor Sr2RuO4. Measurements were performed as a function of temperature T and magnetic fields H of various orientations. Linear decrease of kappa (100)/T in T in zero field is found below 1 K, in contrast to nearly constant value in the normal state. Field dependence of kappa (100)/T at 0.3 K in H perpendicular to the plane is qualitatively similar to that for a line-node superconducting state in the low temperature limit. The dependence gives mu H-0(c1) approximate to 8 mT and mu H-0(c2) approximate to 60 mT. In the in-plane fields, the field dependence at low temperatures shows a notable difference from the perpendicular field case. The temperature and field domain of this anomalous behavior is consistent with the existence of another superconducting phase, as proposed recently.