Superconducting order of Sr2RuO4 from a three-dimensional microscopic model

Abstract

We compute and compare even-and odd-parity superconducting order parameters of strontium ruthenate (Sr2RuO4) in the limit of weak interactions, resulting from a fully microscopic threedimensional model including spin-orbit coupling. We find that odd-parity helical and even-parity dwave order are favored for smaller and larger values of the Hund's coupling parameter J, respectively. Both orders are found compatible with specific heat data and the recently-reported nuclear magnetic resonance (NMR) Knight shift drop [A. Pustogow et al. arXiv:1904.00047 (2019]. The chiral p-wave order, numerically very competitive with helical order, sharply conflicts with the NMR experiment.

Distinct reduction of Knight shift in superconducting state of Sr2RuO4 under uniaxial strain

“…The momentum dependent t 2g -orbital projection of the wave function for the α, β and γ bands on the three-dimensional FS was reported [31], which is consistent with the three dimensional (3D) tight binding model constructed in Ref. [37]. The β and γ bands still have significant overlap of xy and one dimensional (1D) orbitals, even though detailed composition depends on k z as shown in Ref.…”

Superconducting subphase and substantial Knight shift in Sr2RuO4

“…The possibility of other types of singlet pairings such as d-wave or extended s-wave can, of course, not be ruled out 33,66,67 , in particular since the sharp variation of H p2 with polar angle cannot be explained with helical pairing.…”

“…Here we investigate a time reversal symmetry preserving helical pairing 28,[33][34][35][36] state under an in-plane magnetic field using a realistic three-dimensional (3D) tightbinding (TB) model. We focus on results from two experimental studies 30,37 to probe the internal symmetry of the Cooper pairs, and report two key findings.…”

Neutron scattering studies on spin fluctuations in Sr2RuO4

“…The new studies of the Knight shift in NMR [16,17] and those of the polarized neutron diffraction [18] reveal an unambiguous drop of the electronic susceptibility that is inconsistent with spin-triplet pairs parallel to Ru layers. Since then, numerous proposals for the superconducting state were made mostly invoking some d-wave state, and the discussion of the superconducting pairing has become very active [19][20][21][22][23][24][25][26]. The observations of broken time-reversal symmetry in muon spin relaxation experiments [27,28] and in measurements of the magnetooptical Kerr effect [29] may require interpretations other than the chiral p-wave scenario.…”