Abstract
We use inelastic neutron scattering to study spin fluctuations in Sr1.8La0.2RuO4, where Lanthanum doping triggers a Lifshitz transition by pushing the van Hove singularity in the γ band to the Fermi energy. Strong spin fluctuations emerge at an incommensurate wave vector Qic=(0.3,0.3), corresponding to the nesting vector between α and β Fermi sheets. The incommensurate antiferromagnetic fluctuations shift toward (0.25,0.25) with increasing energy up to ∼110 meV. By contrast, scatterings near the ferromagnetic wave vectors Q=(1,0) and (1,1) remain featureless at all energies. This contradicts the weak-coupling perspective that suggests a sharp enhancement of ferromagnetic susceptibility due to the divergence of density of states in the associated γ band. Our findings imply that ferromagnetic fluctuations in Sr2RuO4 and related materials do not fit into the weak-coupling paradigm, but instead are quasilocal fluctuations induced by Hund's coupling. This imposes significant constraints for the pairing mechanism involving spin fluctuations.
| Original language | English |
|---|---|
| Article number | L201107 |
| Journal | Physical Review B |
| Volume | 107 |
| Issue number | 20 |
| DOIs | |
| State | Published - May 15 2023 |
| Externally published | Yes |
Funding
This work was supported by the Key Program of the National Natural Science Foundation of China (Grant No. 12234006), the National Key R&D Program of China (Grant No. 2022YFA1403202), and the Shanghai Municipal Science and Technology Major Project (Grant No. 2019SHZDZX01). Q.W. was supported by the CUHK Research Startup Fund (Grant No. 4937150). Y.F. was supported by Xie Jialin Youth Foundation of Institute of High Energy Physics (Grand No. E2546JU2), and National Key R&D Program of China (Grand No. 2022YFA1604104). H.W. acknowledges support from the China National Postdoctoral Program for Innovative Talents (Grant No. BX2021080), China Postdoctoral Science Foundation (Grant No. 2021M700860), the Youth Foundation of the National Natural Science Foundation of China (Grant No. 12204108), and Shanghai Post-doctoral Excellence Program (Grant No. 2021481). The work at SNU was supported by the Institute for Basic Science in Korea (Grant No. IBS-R009-G2). D.T.A. thanks EPSRC-UK (Grant No. EP/W00562X/1). Experiments at PANDA were conducted under proposal numbers 5114 and 5719. Datasets collected at MERLIN spectrometer are available from the ISIS facility, Rutherford Appleton Laboratory data portal .