Magnetic response of Sr2RuO4 : Quasi-local spin fluctuations due to Hund's coupling

Abstract

We study the magnetic susceptibility in the normal state of Sr2RuO4 using dynamical mean-field theory including dynamical vertex corrections. Besides the well known incommensurate response, our calculations yield quasi-local spin fluctuations which are broad in momentum and centered around the Γ point, in agreement with recent inelastic neutron scattering experiments [P. Steffens, et al., Phys. Rev. Lett. 122, 047004 (2019)]. We show that these quasi-local fluctuations are controlled by the Hund's coupling and account for the dominant contribution to the momentumintegrated response. While all orbitals contribute equally to the incommensurate response, the enhanced Γ point response originates from the planar xy orbital.

Neutron scattering studies on spin fluctuations in Sr2RuO4

“…All techniques find almost temperature-independent quasiferromagnetic excitations in pure Sr 2 RuO 4 . This ferromagnetic response agrees qualitatively with a recent dynamical mean-field theory (DMFT) analysis of magnetic fluctuations [57], which finds essentially local magnetic fluctuations superposed on the well-known nesting signal. However, the neutron data disagree with a fully local character as they show a finite q dependence [45].…”

“…We wished to extend this study focusing on the q dependence of the magnetic quasiferromagnetic response. Recent DMFT calculations [57] find evidence for local fluctuations superposing the well-established nesting excitations, which agree qualitatively with the experimental quasiferromagnetic signal. However, while the neutron experiments indicate a finite suppression of the quasiferromagnetic response toward the boundaries of the Brillouin zone, the DMFT calculation obtains an essentially local feature without such a q dependence.…”

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

“…[15]. While recent neutron scattering experiments and DMFT calculations do not support ferromagnetic spin fluctuations giving rise to spin-triplet pairing [42,43], this triplet leads to an anisotropy, but cannot reproduce the >50% drop in the NMR response, with an ∼40% or smaller drop in the NMR response for all field strengths, unlike the OSST pairing. For this odd-parity pairing, the drop in the Knight shift with no SOC is 50%, and the inclusion of SOC decreases the magnitude of the drop.…”

Coexistence of Even- and Odd-Frequency Superconductivity in Correlated Multi-Orbital Systems with Spin-Orbit Coupling

“…By using DFT, we have a well defined Fermi liquid which allows us to study the role of SOC but neglects strong electronic correlations at the one-body level. Although various works have shown their importance for SRO [39][40][41][42][43][44], none of them was able to correctly account for electronic correlations, SOC and temperatures below T FL at the same time. The exactitude of SRO's normal state in its Fermi liquid regime is an ongoing challenge.…”

“…It depends on two parameters: on-site Coulomb repulsion U and Hund's coupling J. In SRO, works based on realistic electronic structures have shown that strong electronic correlations improve considerably the quantitative description of the one-and twobody propagators characterizing its normal state [39][40][41][42][43][44]. In this work, we include strong electronic correlations only at the two-body level through spin and charge fluctuation theory described in Sec.…”