Mobile orbitons in Ca2CuO3: Crucial role of Hund's exchange

We investigate the CuL3 edge resonant inelastic x-ray scattering (RIXS) spectra of a quasi-1D antiferromagnet Ca2CuO3. In addition to the magnetic excitations, which are well-described by the two-spinon continuum, we observe two dispersive orbital excitations, the 3d(xy) and the 3d(yz) orbitons. We carry out a quantitative comparison of the RIXS spectra, obtained with two distinct incident polarizations, with a theoretical model. We show that any realistic spin-orbital model needs to include a finite, but realistic, Hund's exchange J(H) approximate to 0.5 eV. Its main effect is an increase in orbiton velocities, so that their theoretically calculated values match those observed experimentally. Even though Hund's exchange also mediates some interaction between spinon and orbiton, the picture of spin-orbit separation remains intact and describes orbiton motion in this compound.

Heverhagen, J.Universität Stuttgart,University of Stuttgart (author)
Betto, D.Max-Planck Institute für Festkörperforschung,Max-Planck Institute for Solid State Research,European Synchrotron Radiation Facility (ESRF) (author)
Arpaia, Riccardo,1985Politecnico di Milano,Polytechnic University of Milan,Chalmers tekniska högskola,Chalmers University of Technology(Swepub:cth)arpaia (author)
Rossi, M.Stanford University (author)
Di Castro, D.Universita degli Studi di Roma Tor Vergata,University of Rome Tor Vergata (author)
Brookes, N. B.European Synchrotron Radiation Facility (ESRF) (author)
Sala, M. MorettiPolitecnico di Milano,Polytechnic University of Milan (author)
Daghofer, M.Universität Stuttgart,University of Stuttgart (author)
Braicovich, L.European Synchrotron Radiation Facility (ESRF),Politecnico di Milano,Polytechnic University of Milan (author)
Wohlfeld, K.Uniwersytet Warszawski,University of Warsaw (author)
Ghiringhelli, G.Politecnico di Milano,Polytechnic University of Milan (author)
Politecnico di MilanoUniversität Stuttgart (creator_code:org_t)

By the author/editor: Fumagalli, R.; Heverhagen, J.; Betto, D.; Arpaia, Riccardo ...; Rossi, M.; Di Castro, D.; show more...; Brookes, N. B.; Sala, M. Moretti; Daghofer, M.; Braicovich, L.; Wohlfeld, K.; Ghiringhelli, G.; show less...

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NATURAL SCIENCES: NATURAL SCIENCES; and Physical Science ...; and Condensed Matter ...

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