Dresden 2006 – wissenschaftliches Programm
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TT: Tiefe Temperaturen
TT 34: Correlated Electrons: Spin Systems and Itinerant Magnets
TT 34.4: Vortrag
Freitag, 31. März 2006, 11:00–11:15, HSZ 301
Evidence for collective orbital excitations in YVO3 — •E. Benckiser1,2, R. Rückamp1, M. Grüninger2, A.A. Nugroho3, and T.T.M. Palstra3 — 1II. Physikalisches Institut, Universität zu Köln, Germany — 2II. Physikalisches Institut, RWTH Aachen, Germany — 3Materials Science Centre, Rijksuniversiteit Groningen, The Netherlands
The compound YVO3 recently has attracted a lot of interest because of its unusual structural, orbital and magnetic properties [1,2]. The compound undergoes a series of temperature-induced phase transitions accompanied by a change of orbital and magnetic order. Furthermore it has been proposed that YVO3 represents the first realization of a one-dimensional orbital liquid and an orbital Peierls phase, with a transition to an orbitally ordered phase at lower temperatures [3].
We present the optical conductivity σ(ω ) of YVO3 single crystals for energies from 0.1 eV to 1.6 eV and temperatures from 15 K to 300 K. The data have been collected by performing measurements using linearly polarized light with the electric field vector parallel to the crystallographic axes (σa,σb,σc). The results give clear evidence for orbital excitations. In particular the strong polarization and temperature dependence of two peaks observed at 0.3 eV in σc and 0.5 eV in σa are hard to reconcile with an interpretation in terms of local crystal-field excitations. We propose an interpretation in terms of orbitons and discuss a simple model describing a two-orbiton absorption process. [1] Ren et al., Nature 396, 441(1998); [2] Blake et al., PRB 65, 174112 (2002); [3] Ulrich et al., PRL 91, 257202 (2003). Supported by the DFG through SFB 608.