Berlin 2012 – wissenschaftliches Programm
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TT: Fachverband Tiefe Temperaturen
TT 45: Correlated Electrons: Poster Session
TT 45.86: Poster
Donnerstag, 29. März 2012, 15:00–19:00, Poster B
Strong evidence against orbital fluctuations in RVO3 — •Julia Reul1, Agung Nugroho2, Thomas Palstra2, and Markus Grüninger1 — 1Universität zu Köln — 2Rijksuniversiteit Groningen
Spin and orbital degrees of freedom play a decisive role for the low-energy physics of strongly correlated transition-metal oxides. Whereas the spin is a true low-energy degree of freedom with propagating low-energy excitations, it is still questionable if the same holds true for the orbital degree of freedom. In a typical situation the orbitals are strongly coupled to the lattice, which makes it sufficient to consider classical orbitals with rigid orbital order. However, different groups have pointed out that orbital fluctuations may be strong in the 3d2 Mott-Hubbard insulators RVO3 (R =rare earth ion or Y).
Optical spectroscopy offers an efficient method to study the nature of the orbital degree of freedom, because the spectral weight of excitations across the Mott-Hubbard gap depends sensitively on nearest-neighbor spin-spin and orbital-orbital correlations. We study the temperature dependence of the optical spectral weight by means of ellipsometry in the frequency range 0.75 - 5.5 eV. A comparison of our experimental results for R = Y, Gd and Ce with a theory based on a low-energy spin orbital superexchange Hamiltonian [1,2] leads us as to the conclusion of rigid orbital order in RVO3.
G. Khaliullin, P. Horsch, and A. M. Oles, Phys. Rev. B 70, 195103 (2004)
A. M. Oles, G. Khaliullin, P. Horsch, and L. F. Feiner, Phys. Rev. B 72, 214431
(2005)