Muon spin relaxation studies of Sr₂RuO₄ under uniaxial pressure

For two decades, Sr2RuO4 has been discussed as a spin triplet p-wave superconductor, with a chiral order parameter of the form px ± ipy . This order parameter has not been proved yet, however, one key piece of evidence is the observation of an enhanced zero-field muon spin relaxation (μSR) rate in the superconducting state, which implies that the order parameter breaks time-reversal symmetry (TRS). Nevertheless, the absence of any measureable spontaneous magnetization in scanning SQUID studies raises questions about this interpretation. Superconducting critical temperature of Sr2RuO4 has been shown experimentally to be very sensitive to uniaxial pressure, so the changes in the muon spin relaxation rate with uniaxial pressure could provide further information both on the origin of the enhanced muon relaxation rate, and the superconductivity of Sr2RuO4. Therefore, we have developed a uniaxial pressure cell dedicated for μSR. This cell is based on piezoelectric actuators, allowing continuous in situ tuning of the applied pressure. Results from first set of measurements will be presented, anticipating many further applications for the newly developed apparatus.