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arXiv · 1011.1860

Rapidly fluctuating orbital occupancy above the orbital ordering transition in spin-gap compounds

B. Rivas-Murias·H. D. Zhou·J. Rivas·F. Rivadulla
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Abstract

Several spin systems with low dimensionality develop a spin-dimer phase within a molecular orbital below TS, competing with long-range antiferromagnetic order. Very often, preferential orbital occupancy and ordering are the actual driving force for dimerization, as in the so-called orbitally-driven spin-Peierls compounds (MgTi2O4, CuIr2S4, La4Ru2O10, NaTiSi2O6, etc.). Through a microscopic analysis of the thermal conductivity k (T) in La4Ru2O10, we show that the orbital occupancy fluctuates rapidly above TS, resulting in an orbital-liquid state. The strong orbital-lattice coupling introduces dynamic bond-length fluctuations that scatter the phonons to produce a k (T) proportional to T (i.e. glass-like) above TS. This phonon-glass to phonon-crystal transition is shown to occur in other spin-dimer systems, like NaTiSi2O6, pointing to a general phenomenon.

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B. Rivas-Murias, H. D. Zhou, J. Rivas, F. Rivadulla. 2010-11-08. Rapidly fluctuating orbital occupancy above the orbital ordering transition in spin-gap compounds. https://doi.org/10.1103/physrevb.83.165131

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