Evaluation of two-component superconductivity in Sr₂RuO₄ through measurements under uniaxial stress

Sr₂RuO₄ is a famous candidate for two-component superconductivity. In this talk, I will present three contradictions in the evidence on the superconducting order parameter, that have come to light through uniaxial stress measurements. (1) Muon spin rotation measurements show clear stress-induced splitting between the critical temperature and the onset of enhanced muon spin relaxation, following qualitative expectations for two-component order, but no signature of this second transition is resolved in heat capacity under uniaxial stress. (2) Although in-plane uniaxial stress drives a strong increase in the critical temperature, compression along the c-axis suppresses T_c, even though the enhancement in the density of states should be stronger. (3) There is a jump in the shear elastic modulus at T_c, consistent with two-component order, but no corresponding cusp is resolved in the dependence of T_c on uniaxial stress applied along a <110> crystal axis.