Dresden 2011 – wissenschaftliches Programm
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TT: Fachverband Tiefe Temperaturen
TT 41: CE: Spin Systems and Itinerant Magnets 1
TT 41.1: Vortrag
Mittwoch, 16. März 2011, 18:15–18:30, HSZ 105
Orbital fluctuations versus classical orbital order in RVO3 studied via optical spectral weight — •Julia Küppersbusch1, Agung Nugroho2, Thomas Palstra2, and Markus Grüninger1 — 1Universtität zu Köln — 2Rijksuniversiteit Groningen
Spin and orbital degrees of freedom play a decisive role in 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 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. By comparing our experimental results for R = Y, Gd, and Ce
with a theory which calculates the
temperature dependence of the optical spectral weight based on a low-energy
spin-orbital superexchange Hamiltonian [1,2], we draw a
conclusion about the nature of the orbital degree of freedom in RVO3.
G. Khaliullin, P. Horsch, and A.M. Oles, Phys. Rev. B 70, 195103 (2004)
A. M. Oles et al. Phys. Rev. B 72, 214431 (2005)