Scanning SQUID Susceptometry of Sr₂RuO₄ Under Uniaxial Pressure

Anisotropic strain, as applied through uniaxial pressure, is expected to lift the degeneracy between the components of the proposed p_x±ip_y superconducting order parameter of Sr₂RuO₄. However, neither the resulting split transition nor the expected linear cusp in superconducting transition temperature, T_C, at low strain has been observed to date. Furthermore, measurements of the critical field anisotropy suggest that the order parameter may be of even parity at high values of anisotropic strain, where T_C is strongly enhanced. In this study, we will use scanning SQUID susceptometry to obtain measurements of T_C and changes in the penetration depth, λ, as a function of temperature and uniaxial pressure. We image strain inhomogeneity by mapping T_C with micron-scale spatial resolution and perform local measurements of the superfluid density in homogeneous regions. Penetration depth measurements yield insight into the symmetry of the order parameter and its dependence on strain.