Probing orbital fluctuations inRVO3(R=<

Abstract

Take-down policy If you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediately and investigate your claim.Downloaded from the University of Groningen/UMCG research database (Pure): http://www.rug.nl/research/portal. For technical reasons the number of authors shown on this cover page is limited to 10 maximum. We study optical excitations across the Mott gap in the multiorbital Mott-Hubbard insulators RVO 3 . The multipeak structure observed in the optical conductivity can be described consistently in terms of the different 3d 3 multiplets or upper Hubbard bands. The spectral weight is very sensitive to nearest-neighbor spin-spin and orbital-orbital correlations and thus shows a pronounced dependence on both temperature and polarization. Comparison with theoretical predictions based on either rigid orbital order or strong orbital fluctuations clearly rules out that orbital fluctuations are strong in RVO 3 . Both the line shape and the temperature dependence give clear evidence for the importance of excitonic effects.

Orbital superexchange and crystal field simultaneously at play in YVO3: Resonant inelastic x-ray scattering at the VLedge and the OKedge

“…The steep increase of the RIXS signal at 4.5 eV for E in = 530.1 eV at the O K edge is in good agreement with the onset of charge-transfer excitations observed in the optical conductivity. 30,51,52 However, the large intensity, exceeding the intensity of the elastic peak, points towards x-ray fluorescence emission, possibly superimposed by the charge-transfer excitations mentioned above.…”

“…32 For YVO 3 , strong orbital fluctuations have been ruled out recently by optical data for the Mott-Hubbard excitations. 30 Another argument against a two-orbiton interpretation of the peak at 0.2 eV is the observation of a two-orbiton peak at 0.4 eV in RIXS at the O K edge (see Sec. IV D) and in the optical conductivity.…”

“…21 A shift of the excitation energy can be explained in a crystal-field scenario by a change of the crystal structure and thus of the crystal field, and in a superexchange-based scenario by a change of the orbital order. 28,70 However, the orbital order changes dramatically between the different ordered phases and the orbitally disordered phase above 200 K, and orbital fluctuations are only weak above 200 K. 30 Accordingly, spin-orbital superexchange models predict a significant change of the excitation energies across the phase transitions between the different phases. 28,70 In contrast, the observed shifts of 10-40 meV are much smaller than the excitation energy of 0.1-0.2 eV.…”

“…3 However, a recent study of the optical excitations across the Mott-Hubbard gap rules out that orbital fluctuations are strong in RVO 3 . 30 Some of us reported the observation of orbital excitations in the optical conductivity of YVO 3 . 21 An optical absorption band at 0.4 eV for polarization of the electric field E c has been attributed to the exchange of orbitals on adjacent sites, i.e., to the direct excitation of two orbitons.…”

Y1−xLaxVO3: Effects of doping on orbital ordering

“…The insulating Y 1−x La x VO 3 , a JT active system, has been of considerable interest due to its complex phase diagram [5][6][7][8][9][10][11][12][13] associated with orbital physics [14][15][16][17][18][20][21][22]. With cooling, the parent compound, YVO 3 , undergoes a transition to a G-type orbital ordering (anti-phase ordering along the c-axis, G-OO) at T OO ∼ 200 K, followed by a C -type antiferromagnetic spin ordering at T N ∼ 116 K (C-SO) and finally to an orbital flipping transition at T CG ∼ 77 K with C -type orbital ordering (in-phase ordering along the c-axis, C-OO) and G-type spin ordering (G-SO) [19,20].…”