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Probing magnons with X-rays. Luuk Ament In collaboration with Fiona Forte & Jeroen van den Brink. Lorentz-Institute, Leiden University. Indirect RIXS. Synchrotron radiation. Interesting sample. 4p. w res (5-10 keV). 1s. Why RIXS?. Second order process Momentum dependence

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probing magnons with x rays

Probing magnons with X-rays

Luuk Ament

In collaboration with Fiona Forte & Jeroen van den Brink

Lorentz-Institute, Leiden University

indirect rixs
Indirect RIXS

Synchrotron radiation

Interestingsample

4p

wres (5-10 keV)

1s

why rixs
Why RIXS?
  • Second order process
  • Momentum dependence
  • Supplementary to neutron scattering
la 2 cuo 4
La2CuO4
  • Perovskite layers of CuO2:
la 2 cuo 41
La2CuO4
  • Perovskite layers of CuO2:
  • Cu 3d eg holes behave as Heisenberg spins:
  • Ground state is antiferromagnetically ordered
la 2 cuo 42
La2CuO4
  • Perovskite layers of CuO2:
  • Cu 3d eg holes behave as Heisenberg spins:
  • Ground state is antiferromagnetically ordered
  • Collective excitations: magnons
what happens in rixs
What happens in RIXS?
  • Actually, the Heisenberg model can be derived from a Hubbard model in the limit U >> t with J = 2t2/U
  • The 1s core-hole creates a potential which effectively changes U, and therefore J.
what happens in rixs1
What happens in RIXS?
  • Actually, the Heisenberg model can be derived from a Hubbard model in the limit U >> t with J = 2t2/U
  • The 1s core-hole creates a potential which effectively changes U, and therefore J.
calculation
Calculation
  • Kramers-Heisenberg relation gives the cross section:
calculation1
Calculation
  • Kramers-Heisenberg relation gives the cross section:
  • Approximate  >> En
calculation2
Calculation
  • Kramers-Heisenberg relation gives the cross section:
  • Approximate  >> En
  • Hamiltonians conserve Sz: only 2-magnon processes!
results
Results
  • Good agreement with recent experiments by John Hill et al. at Argonne:
    • Vanishing intensity at q = (0,0) and q = (,)
    • Peak in intensity at q = (,0) and  = 500 meV

Theory

Theory + experimental resolution

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