Universal heat transport in Sr2RuO4 -: art. no. 227004

We present the temperature dependence of the thermal conductivity kappa(T) of the unconventional superconductor Sr2RuO4 down to low temperatures (similar to100 mK). In the T-->0 K limit we found a finite residual term in kappa/T, providing clear evidence for the superconducting state with an unconventional pairing. The residual term remains unchanged for samples with different T-c, demonstrating the universal character of heat transport in this spin-triplet superconductor. The low-temperature behavior of kappa suggests the strong impurity scattering with a phase shift close to pi/2. A criterion for the observation of universality is experimentally deduced.