Thermal conductivity of superconductingSr2RuO4in oriented magnetic fields

Abstract

We report in-plane thermal conductivity along [100] direction, ${\ensuremath{\kappa}}_{100},$ of high quality single crystals ${(T}_{\mathrm{c}}=1.44 \mathrm{K})$ of unconventional superconductor ${\mathrm{Sr}}_{2}{\mathrm{RuO}}_{4}.$ Measurements were performed as a function of temperature T and magnetic fields H of various orientations. Linear decrease of ${\ensuremath{\kappa}}_{100}/T$ in T in zero field is found below 1 K, in contrast to nearly constant value in the normal state. Field dependence of ${\ensuremath{\kappa}}_{100}/T$ 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 ${\ensuremath{\mu}}_{0}{H}_{\mathrm{c}1}\ensuremath{\approx}8 \mathrm{mT}$ and ${\ensuremath{\mu}}_{0}{H}_{\mathrm{c}2}\ensuremath{\approx}60 \mathrm{mT}.$ 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.