"Micron-scale measurements of low anisotropic strain response of local Tc in Sr2 RuO4"

Christopher A. Watson: Alexandra S. Gibbs, Andrew P. Mackenzie, Clifford W. Hicks, and Kathryn A. Moler; Physical Review B, 09/26/18.

Additional Authors: Alexandra S. Gibbs, Andrew P. Mackenzie, Clifford W. Hicks, and Kathryn A. Moler

Abstract:

Strontium ruthenate (Sr2RuO4) is a multiband superconductor that displays evidence of topological superconductivity, although a model of the order parameter that is consistent with all experiments remains elusive. We integrated a piezoelectric-based strain apparatus with a scanning superconducting quantum interference device microscope to map the diamagnetic response of single-crystal Sr2RuO4 as a function of temperature, uniaxial pressure, and position with micron-scale spatial resolution. We thereby obtained local measurements of the superconducting transition temperature Tc vs anisotropic strain ε with sufficient sensitivity for comparison to theoretical models that assume a uniform px±ipy order parameter. We found that Tc varies with position and that the locally measured Tc vs ε curves are quadratic (Tc∝ε2), as allowed by the C4 symmetry of the crystal lattice. We did not observe the low-strain linear cusp (Tc∝|ε|) that would be expected for a two-component order parameter such as px±ipy. These results provide new input for models of the order parameter of Sr2RuO4.