634 research outputs found
Spin chain in magnetic field: limitations of the large-N mean-field theory
Motivated by the recent success in describing the spin and orbital spectrum
of a spin-orbital chain using a large-N mean-field approximation [Phys. Rev. B
91, 165102 (2015)], we apply the same formalism to the case of a spin chain in
the external magnetic field. It occurs that in this case, which corresponds to
N=2 in the approximation, the large-N mean-field theory cannot qualitatively
reproduce the spin excitation spectra at high magnetic fields, which polarize
more than 50% of the spins in the magnetic ground state. This, rather
counterintuitively, shows that the physics of a spin chain can under some
circumstances be regarded as more complex than the physics of a spin-orbital
chain.Comment: 4 pages, 3 figures; appeared in the proceedings of the European
Conference "Physics of Magnetism" (2014
Determining the Electron-Phonon Coupling Strength in Correlated Electron Systems from Resonant Inelastic X-ray Scattering
We show that high resolution Resonant Inelastic X-ray Scattering (RIXS)
provides direct, element-specific and momentum-resolved information on the
electron-phonon (e-p) coupling strength. Our theoretical analysis demonstrates
that the e-p coupling can be extracted from RIXS spectra by determining the
differential phonon scattering cross section. An alternative, very direct
manner to extract the coupling is to use the one and two-phonon loss ratio,
which is governed by the e-p coupling strength and the core-hole life-time.
This allows measurement of the e-p coupling on an absolute energy scale.Comment: 4 pages, 3 figure
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