Presented By: Department of Physics
Special QC-CM Seminar | Magnetic susceptibility and pairing in Sr2RuO4 from the dynamical two-particle vertex
Hugo U.R. Strand (Orebro University, Sweden)
Strontium ruthenate (Sr2RuO4) is a strongly correlated complex oxide for which crystals with exquisite purity can be prepared, allowing for a wealth of experimental studies. It displays unconventional superconductivity, Hund's metal physics, and an incommensurate antiferromagnetic spin response.
To understand the interplay of collective spin excitations and the Fermi liquid quasi particles we have performed density functional theory and dynamical mean field theory calculations of the susceptibility using the Bethe-Salpeter equation [1]. Obtaining qualitative agreement with inelastic neutron scattering experiments [2].
The crucial importance of local quantum fluctuations in the vertex is established by comparison with the static random phase approximation. We also study the spin-orbit driven anisotropy and disentangle the orbital contributions. Our findings confirm that this material is close to a magnetic instability, as revealed by its sensitivity to impurity substitutions. Comparing the local and momentum dependent response, we pinpoint signatures of Hund's metal physics in the inelastic neutron spectra.
Using the generalized susceptibility the particle-particle irreducible vertex is constructed and combined with the linearized Eliashberg equation to compute the superconducting gap function [3]. The two leading superconducting instabilities are compared to a range of experiments, singling out the two-component inter-orbital singlet state as the favoured gap function symmetry. The two weakly dispersive components pair the in-plane xy orbital and the out-of-plane xz and yz orbital, respectively, and are primarily driven by inter-orbital spin fluctuations.
[1] H. U.R. Strand, et al., Phys. Rev. B 100, 125120 (2019)
[2] P. Steffens, et al., Phys. Rev. Lett. 122, 047004 (2019)
[3] S. Käser, et al., Phys. Rev. B 105, 155101 (2022)
To understand the interplay of collective spin excitations and the Fermi liquid quasi particles we have performed density functional theory and dynamical mean field theory calculations of the susceptibility using the Bethe-Salpeter equation [1]. Obtaining qualitative agreement with inelastic neutron scattering experiments [2].
The crucial importance of local quantum fluctuations in the vertex is established by comparison with the static random phase approximation. We also study the spin-orbit driven anisotropy and disentangle the orbital contributions. Our findings confirm that this material is close to a magnetic instability, as revealed by its sensitivity to impurity substitutions. Comparing the local and momentum dependent response, we pinpoint signatures of Hund's metal physics in the inelastic neutron spectra.
Using the generalized susceptibility the particle-particle irreducible vertex is constructed and combined with the linearized Eliashberg equation to compute the superconducting gap function [3]. The two leading superconducting instabilities are compared to a range of experiments, singling out the two-component inter-orbital singlet state as the favoured gap function symmetry. The two weakly dispersive components pair the in-plane xy orbital and the out-of-plane xz and yz orbital, respectively, and are primarily driven by inter-orbital spin fluctuations.
[1] H. U.R. Strand, et al., Phys. Rev. B 100, 125120 (2019)
[2] P. Steffens, et al., Phys. Rev. Lett. 122, 047004 (2019)
[3] S. Käser, et al., Phys. Rev. B 105, 155101 (2022)
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