Regensburg 2010 – wissenschaftliches Programm
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TT: Fachverband Tiefe Temperaturen
TT 22: CE: Spin Systems and Itinerant Magnets
TT 22.6: Vortrag
Mittwoch, 24. März 2010, 10:45–11:00, H21
Orbitally induced string formation in the spin-orbital polarons — •Krzysztof Wohlfeld1, Andrzej M. Oles2,3, and Peter Horsch3 — 1IFW Dresden, Germany — 2Jagellonian University, Poland — 3Max-Planck-Institut für Festkörperforschung, Germany
We study the spectral function of a single hole doped into an ab plane of a Mott insulator LaVO3 with antiferromagnetic (AF) spin order of S=1 spins accompanied by alternating orbital (AO) order of active {yz,zx} orbitals [1]. Starting from the respective t-J model, with spin-orbital superexchange and effective three-site hopping terms, we derive the polaron Hamiltonian and show that a hole couples simultaneously to the collective excitations of the AF/AO phase, magnons and orbitons. Next, we solve this polaron problem using the self-consistent Born approximation and find a stable quasiparticle solution — a spin-orbital polaron. We show that the spin-orbital polaron resembles the orbital polaron found in eg systems, as e.g. in K2CuF4 or (to some extent) in LaMnO3, and that the hole may be seen as confined in a string-like potential. However, the spins also play a crucial role in the formation of this polaron — we explain how the orbital degrees of freedom: (i) confine the spin dynamics acting on the hole as the classical Ising spins, and (ii) generate the string potential which is of the joined spin-orbital character. Finally, we discuss the impact of the results presented here on the understanding of the phase diagrams of the lightly doped cubic vanadates.
[1] K. Wohlfeld, A. M. Oleś, and P. Horsch, Phys. Rev. B 79, 224433 (2009).