Probing magnons with X-rays. Kramers-Heisenberg relation:. Energy conservation. Dipole operator. Intermediate states. with. Detuning from resonance. Core-hole exists a short time: ≈ 2-3 eV.
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Core-hole exists ashort time: ≈ 2-3 eV
Core-hole creates local potential from which electrons of the solid are scattered. System can be left behind in excited state. One measures elementary excitations of the solid!
J modified bycore-hole potential
Conclusions & Outlook
F. Forte, L.J.P. Ament, J. van den Brink
Instituut-Lorentz, Universiteit Leiden, P.O. Box 9506, 2300 RA Leiden, The Netherlands
Momentum transfer q & Energy loss
Unoccupied valence level
wres (5-10 KeV)
Magnetic RIXS on La2CuO4
Theory applied to La2CuO4
La2CuO4: 3d electrons on Cu form Mott-Hubbard insulator effective Heisenberg Hamiltonian:
qin , win
qout , wout qin, win
Elementary excitations are magnons.
Conservation of Sz only 2-magnon processes allowed!
Core-hole modifies superexchange interaction Jij
> En: we can resum Afi and retain the leading order term in J’/:
ExperimentTheoryTheory + exp. resolution
a 4-spin correlation function! We used linear spin-wave theory to obtain the spectra.
We established a general procedure to find indirect RIXS spectra. Application to La2CuO4 shows:
1. Only 2-magnon processes allowed2. Quantitative agreement with experiments3. RIXS complements neutron scattering (2-spin correlation functions)
The next step will be to apply this theory to other elementary excitations like orbital waves.
At q = (0,0) there is no energy loss: RIXS intensity = 0.
Experiments: J.P. Hill et al.1,magnetic parameters from neutron scattering2.
No free magnetic parameters!
2Coldea et al. Phys. Rev. Lett. 86, 5377 (2001)