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Andrzej M. Oles, Jesko Sirker, Alexander Herzog, Peter Horsch and Giniyat Khaliullin The mechanism responsible for the onset of C-type antiferromagnetic (AF) order accompanied by G-type orbital order in the RVO3 perovskites has been understood recently [1], yet the observed dimerization along the ferromagnetic (FM) direction in YVO3 [2] remains puzzling. Here we demonstrate that in FM spin chains a Peierls dimerization can occur [3], activated by thermal fluctuations, but not at zero temperature as in AF chains. The dimer order parameter and entanglement measures are studied as functions of the modulation of the magnetic exchange interaction and temperature. We show that a modified spin-wave theory is capable to describe results obtained by transfer matrix renormalization group in a wide temperature range and up to large dimerization. We discuss the case where a periodic modulation is caused by spin-phonon coupling and the case where it is induced by the orbital degree of freedom, i.e., the orbital Peierls dimerization. The importance of the latter for a number of transition metal oxides including YVO3 is highlighted. [1] P. Horsch, A.M. Oles, L.F. Feiner, G. Khaliullin, Phys. Rev. Lett. 100, 167205 (2008). [2] C. Ulrich, G. Khaliullin, J. Sirker et al., Phys. Rev. Lett. 91, 257202 (2003). [3] J. Sirker, A. Herzog, A.M. Oles, P. Horsch, Phys. Rev. Lett. 101, 157204 (2008). |
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