Skip to main content

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

Cornell Affiliated Author(s)


Sayak Ghosh
Arkady Shekhter
F. Jerzembeck
N. Kikugawa
Dmitry Sokolov
Manuel Brando
A. Mackenzie
Clifford Hicks
B. Ramshaw


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 and dx2−y2,gxy(x2−y2), are now the prime candidates for the order parameter of Sr2RuO4. © 2020, The Author(s), under exclusive licence to Springer Nature Limited.

Date Published


Nature Physics





Number of Pages





Group (Lab)

Brad Ramshaw Group

Download citation