[Paper] Constraints on a split superconducting transition under uniaxial strain in Sr$_2$RuO$_4$

日本語/English

Our study of scanning SQUID susceptometry on Sr$_2$RuO$_4$ under uniaxial strain was published in Physical Review B, selected as the Editors' Suggestion.

Strontium ruthenate (Sr$_2$RuO$_4$) is a material that has intrigued scientists due to its unique superconducting properties. One of the burning questions is whether its superconducting order parameter has a single component or two degenerate ones. If there were two components, applying a uniaxial strain should make these components separate into two distinct phases.

To figure this out, we used scanning SQUID susceptometry, which is sensitive to changes in the property known as the London penetration depth. This property provides insights into the superconducting state of the material. When we applied the strain, we were looking for a second transition, which would suggest the presence of two components in the order parameter. 

Recent muSR measurements observed the time-reversal symmetry breaking (TRSB) in Sr$_2$RuO$_4$ under strain (Grinenko et al., Nat. Phys. 17, 748 (2021)). However, even in temperatures where muSR studies hinted there might be a second transition, we found no evidence of it. Our results suggest that if there were a second transition, it would change the zero temperature superfluid density by less than 1%, which makes it highly unlikely.

This study constrains theories that strontium ruthenate's superconducting order parameter has two degenerate components. It's a significant step forward in understanding the mysterious properties of this material.

E. Mueller, Y. Iguchi, C. Watson, C. Hicks, Y. Maeno, and K. A. Moler
Constraints on a split superconducting transition under uniaxial strain in Sr$_2$RuO$_4$ from scanning SQUID microscopy
Phys. Rev. B 108, 144501 (2023). [Editors' Suggestion]