Unsplit superconducting and time reversal symmetry breaking transitions in Sr$_2$RuO$_4$ under hydrostatic pressure and disorder

Vadim Grinenko; Debarchan Das; Ritu Gupta; Bastian Zinkl; Naoki Kikugawa; Yoshiteru Maeno; Clifford W. Hicks; Hans-Henning Klauss; Manfred Sigrist; Rustem Khasanov

doi:10.1038/s41467-021-24176-8

paper

Unsplit superconducting and time reversal symmetry breaking transitions in Sr $_{2}$ RuO $_{4}$ under hydrostatic pressure and disorder

arXiv:2103.03600 · doi:10.1038/s41467-021-24176-8

Abstract

There is considerable evidence that the superconducting state of Sr $_{2}$ RuO $_{4}$ breaks time reversal symmetry. In the experiments showing time reversal symmetry breaking its onset temperature, $T_{TRSB}$ , is generally found to match the critical temperature, $T_{c}$ , within resolution. In combination with evidence for even parity, this result has led to consideration of a $d_{x z} \pm i d_{y z}$ order parameter. The degeneracy of the two components of this order parameter is protected by symmetry, yielding $T_{TRSB} = T_{c}$ , but it has a hard-to-explain horizontal line node at $k_{z} = 0$ . Therefore, $s \pm i d$ and $d \pm i g$ order parameters are also under consideration. These avoid the horizontal line node, but require tuning to obtain $T_{TRSB} \approx T_{c}$ . To obtain evidence distinguishing these two possible scenarios (of symmetry-protected versus accidental degeneracy), we employ zero-field muon spin rotation/relaxation to study pure Sr $_{2}$ RuO $_{4}$ under hydrostatic pressure, and Sr $_{1.98}$ La $_{0.02}$ RuO $_{4}$ at zero pressure. Both hydrostatic pressure and La substitution alter $T_{c}$ without lifting the tetragonal lattice symmetry, so if the degeneracy is symmetry-protected $T_{TRSB}$ should track changes in $T_{c}$ , while if it is accidental, these transition temperatures should generally separate. We observe $T_{TRSB}$ to track $T_{c}$ , supporting the hypothesis of $d_{x z} \pm i d_{y z}$ order.

arXiv comment14 pages, 8 Figures

Unsplit superconducting and time reversal symmetry breaking transitions in Sr $_{2}$ RuO $_{4}$ under hydrostatic pressure and disorder

Abstract

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Unsplit superconducting and time reversal symmetry breaking transitions in Sr2​RuO4​ under hydrostatic pressure and disorder

Abstract

References in corpus (40)

Cited by in corpus (45)

Unsplit superconducting and time reversal symmetry breaking transitions in Sr $_{2}$ RuO $_{4}$ under hydrostatic pressure and disorder