Direct evidence for the absence of coupling between shear strain and superconductivity in Sr<sub>2</sub>RuO<sub>4</sub>.
basic_science · Level V
Where this comes from
- Record sourced from PubMed, PMID 41402298.
- Also identified by DOI 10.1038/s41467-025-67307-1 and PMC identifier 12820312.
- Licence recorded as CC BY-NC-ND.
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Abstract
The superconducting symmetry of Sr<sub>2</sub>RuO<sub>4</sub> has been intensely debated for many years. A crucial controversy recently emerged between shear-mode ultrasound experiments, which suggest a two-component order parameter, and some uniaxial pressure experiments that suggest a one-component order parameter. To resolve this controversy, we use a new approach to directly apply three different kinds of shear strain to single crystals of Sr<sub>2</sub>RuO<sub>4</sub> and investigate the coupling to superconductivity. After characterising the strain by optical imaging, we observe variations of the transition temperature T<sub>c</sub> smaller than 10 mK%<sup>-1</sup> as measured by low-frequency magnetic susceptibility, indicating that shear strain has little to no coupling to superconductivity. Our results are consistent with a one-component order parameter model, but such a model cannot consistently explain other experimental evidence such as time-reversal symmetry breaking, superconducting domains, and horizontal line nodes, thus calling for alternative interpretations.