Split superconducting and time-reversal symmetry-breaking transitions, and magnetic order in Sr$_2$RuO$_4$ under uniaxial stress

Vadim Grinenko; Shreenanda Ghosh; Rajib Sarkar; Jean-Christophe Orain; Artem Nikitin; Matthias Elender; Debarchan Das; Zurab Guguchia; Felix Brückner; Mark E. Barber; Joonbum Park; Naoki Kikugawa; Dmitry A. Sokolov; Jake S. Bobowski; Takuto Miyoshi; Yoshiteru Maeno; Andrew P. Mackenzie; Hubertus Luetkens; Clifford W. Hicks; Hans-Henning Klauss

doi:10.1038/s41567-021-01182-7

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arXiv · 2001.08152

Split superconducting and time-reversal symmetry-breaking transitions, and magnetic order in Sr$_2$RuO$_4$ under uniaxial stress

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Abstract

Among unconventional superconductors, Sr$_2$RuO$_4$ has become a benchmark for experimentation and theoretical analysis because its normal-state electronic structure is known with exceptional precision, and because of experimental evidence that its superconductivity has, very unusually, a spontaneous angular momentum, i.e. a chiral state. This hypothesis of chirality is however difficult to reconcile with recent evidence on the spin part of the order parameter. Measurements under uniaxial stress offer an ideal way to test for chirality, because under uniaxial stress the superconducting and chiral transitions are predicted to split, allowing the empirical signatures of each to be identified separately. Here, we report zerofield muon spin relaxation (ZF-$\mu$SR) measurements on crystals placed under uniaxial stresses of up to 1.05 GPa. We report a clear stress-induced splitting between the onset temperatures of superconductivity and time-reversal symmetry breaking, consistent with qualitative expectations for chiral superconductivity. We also report the appearance of unexpected bulk magnetic order under a uniaxial stress of ~ 1.0 GPa in clean Sr$_2$RuO$_4$.

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Vadim Grinenko, Shreenanda Ghosh, Rajib Sarkar, Jean-Christophe Orain, Artem Nikitin, Matthias Elender, Debarchan Das, Zurab Guguchia, Felix Brückner, Mark E. Barber, Joonbum Park, Naoki Kikugawa, Dmitry A. Sokolov, Jake S. Bobowski, Takuto Miyoshi, Yoshiteru Maeno, Andrew P. Mackenzie, Hubertus Luetkens, Clifford W. Hicks, Hans-Henning Klauss. 2020-01-22. Split superconducting and time-reversal symmetry-breaking transitions, and magnetic order in Sr$_2$RuO$_4$ under uniaxial stress. https://doi.org/10.1038/s41567-021-01182-7

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