Superconducting Instability From Spin Fluctuations in Sr₂RuO₄

The symmetry of the superconducting condensate in Sr₂RuO₄ remains controversial after recent experiments overturned the dominant chiral p-wave paradigm: NMR leaves almost no room for a triplet component and ultrasound experiments put very stringent constraints on the superconducting order parameter which is deemed to comprise two components[1,2,3]. At the same time, specific heat finds no evidence for a split transition under uniaxial strain [4] in sharp contrast to the findings of muon spin rotation[5].

We explore which superconducting order parameters are favorable from the perspective of spin-fluctuation mediated pairing, taking into account the three Ru orbitals, a sizable spin-orbit coupling, longer range Coulomb interaction as well as three-dimensional effects. A full self-consistent solution of the gap sheds light on the propensity to time-reversal breaking superconducting order based on the near-degeneracy of symmetry-distinct pairing states and we will discuss effects due to strain and impurities.

 

 

[1] A. Pustogow et al., Nature 574, 72 (2019)

[2] S. Ghosh et al., Nat. Phys. 17, 199 (2021)

[3] S. Benhabib et al., Nat. Phys. 17, 194 (2021)

[4] Y.-S. Li et al, PNAS 118, 10 (2021)

[5] V. Grinenko et al, Nat. Phys. 17, 748 (2021)