Anisotropic spin fluctuations in Sr2RuO4 : Role of spin-orbit coupling and induced strain

Abstract

We analyze the spin anisotropy of the magnetic susceptibility of Sr2RuO4 in presence of spin-orbit coupling and anisotropic strain using quasi-two-dimensional tight-binding parametrization fitted to the ARPES results. Similar to the previous observations we find the in-plane polarization of the low q magnetic fluctuations and the out-of-plane polarization of the incommensurate magnetic fluctuation at the nesting wave vector Q1 = (2/3π, 2/3π) but also nearly isotropic fluctuations near Q2 = (π/6, π/6). Furthermore, one finds that apart from the high-symmetry direction of the tetragonal Brillouin zone the magnetic anisotropy is maximal, i.e. χ xx = χ yy = χ zz . This is the consequence of the orbital anisotropy of the xz and yz orbitals in the momentum space. We also study how the magnetic anisotropy evolves in the presence of the strain and find strong Ising-like ferromagnetic fluctuations near the Lifshitz transition for the xy-band.

Anisotropy of magnetic interactions and symmetry of the order parameter in unconventional superconductor Sr2RuO4

“…This simple estimate emphasizes the importance of getting a handle of the type and scale of relativistic effects in Sr 2 RuO 4 . So far all efforts in this direction have been performed either within simplified models or by educated guesses from the experiment [30][31][32][33][34]. The goal of this paper is to address the issue from a first principle perspective.…”

Knight Shift and Leading Superconducting Instability from Spin Fluctuations in Sr2RuO4

“…In this case, the usual spin-fluctuation exchange pairing mechanism [12] would be expected to lead to even parity spin-singlet solutions rather than odd parity spin-triplet states. The situation is further complicated by the multi-orbital nature of the electronic states [7,13], as well as sizeable spin-orbit coupling [14][15][16][17], resulting in significant magnetic anisotropy of the spin fluctuations in this material [10,18,19], which complicate theoretical analysis. Furthermore, as the main belief was that Sr 2 RuO 4 supported a spin-triplet superconducting state, most theories focused on such solutions.…”

“…As in Ref. 19 we parametrize the band by {t 1 , t 2 , t 3 , t 4 , t 5 } = {88, 9, 80, 40, 5} meV with g(k) = 0 and the chemical potential of the xz, yz orbitals µ = 109 meV. Below, µ xy is allowed to vary slightly from µ to map out the effect of a different crystal field, motivated by a sensitivity of the superconducting instability to the proximity of the xy orbital Fermi surface states to the van Hove saddle points.…”

Superconducting Symmetries of Sr2RuO4 from First-Principles Electronic Structure

“…The multi-orbital nature of the superconductivity in SRO complicates the analysis. Numerous studies have attempted to characterize the symmetry of SRO superconducting order parameter along with its dominant orbital host [23][24][25][26][27][28][29][30][31][32][33][34][35], yet this discussion remains open [22]. Here, we investigate the leading superconducting instabilities starting from a correlated electronic structure obtained from a first-principle approach.…”