Thermodynamic evidence for a two-component superconducting order parameter in Sr2RuO4

By Sayak Ghosh, A. Shekhter, F. Jerzembeck, N. Kikugawa, D. Sokolov, M. Brando, A. Mackenzie, C. Hicks, B. Ramshaw. Nature Physics, 2020

173 citations recorded by the source corpus.

Sr2RuO4 has stood as the leading candidate for a spin-triplet superconductor for 26 years1. However, recent NMR experiments have cast doubt on this candidacy2,3 and it is difficult to find a theory of superconductivity that is consistent with all experiments. The order parameter symmetry for this material therefore remains an open question. Symmetry-based experiments are needed that can rule out broad classes of possible superconducting order parameters. Here, we use resonant ultrasound spectroscopy to measure the entire symmetry-resolved elastic tensor of Sr2RuO4 through the superconducting transition. We observe a thermodynamic discontinuity in the shear elastic modulus c66, which implies that the superconducting order parameter has two components. A two-component p-wave order parameter, such as px + ipy, naturally satisfies this requirement. As this order parameter appears to have been precluded by recent NMR experiments, we suggest that two other two-component order parameters, namely {dxz,dyz}\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\{{d}_{xz},{d}_{yz}\}$$\end{document} and {dx2−y2,gxy(x2−y2)}\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\{{d}_{{x}^{2}-{y}^{2}},{g}_{xy({x}^{2}-{y}^{2})}\}$$\end{document}, are now the prime candidates for the order parameter of Sr2RuO4. Ultrasound measurements show that the superconducting order parameter in strontium ruthenate must have two components.

Subfields: Atomic and Molecular Physics, and Optics, Condensed Matter Physics, Electronic, Optical and Magnetic Materials

View Paper: https://www.semanticscholar.org/paper/489fd8aa91e0909f825ccdb23512bcf395572668