Berlin 2012 – scientific programme

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TT: Fachverband Tiefe Temperaturen

TT 45: Correlated Electrons: Poster Session

TT 45.89: Poster

Thursday, March 29, 2012, 15:00–19:00, Poster B

Mott-Hubbard excitations in hole doped RTiO₃ (R= rare earth ion or Y) studied via spectroscopic ellipsometry — •Ignacio Vergara, Julia Reul, Alexander Gössling, Alexander Komarek, and Markus Grüninger — Universität zu Köln

Hole doping of the 3d¹ Mott-Hubbard insulators RTiO₃ (R= rare earth ion or Y) leads to an interesting phase diagram including spin, charge and orbital order. Temperature dependent (20 K<T<500 K) spectroscopic ellipsometry (0.75 - 5.5 eV) offers a very sensitive method to study these phenomena as the Mott-Hubbard excitations from the lower to the upper Hubbard-Band |dⁿ ⟩|dⁿ ⟩→ |dⁿ⁺¹ ⟩|dⁿ⁻¹ ⟩ are sensitively dependent on nearest-neighbor spin-spin and orbital-orbital correlations.

The optical spectra of the undoped 3d¹ compounds RTiO₃ show a complex multipeak structure which has been attributed to the Mott-Hubbard excitations into the different 3d² multiplets, while the temperature dependence has been analyzed on the basis of nearest-neighbor spin-spin correlations [1]. We now study the impact of hole doping on the optical spectra. In a perfect charge ordered scenario of a half doped compound, the hopping of an electron to the neighboring lattice site should not result in a double occupancy. Thus, instead of the Hubbard energy U the excitation should only cost the nearest-neighbor repulsion V.
A. Gössling et al., Phys. Rev. B 78, 075122 (2008)