Spin--orbital physics in transition metal oxides

Abstract

We present the main features of the spin-orbital superexchange which describes the magnetic and optical properties of Mott insulators with orbital degrees of freedom. In contrast to the SU(2) symmetry of spin superexchange, the orbital part of the superexchange obeys the lower cubic symmetry of the lattice and is intrinsically frustrated. This intrinsic frustration and spin-orbital entanglement induce enhanced quantum fluctuations, and we point out a few situations where this leads to disordered states. Strong coupling between the spin and orbital degrees of freedom is discussed on the example of the $R$VO${}_3$ perovskites, with $R$ standing for rare-earth ion, La,...,Lu. We explain the observed evolution of the orbital $T_{\mathrm{OO}}$ and Néel $T_{N1}$ transition temperature in the $R$VO${}_3$ series with decreasing ionic radius $r_R$. A few open problems and the current directions of research in the field of spin-orbital physics are pointed out.

19 pages, 5 figures

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Cited by in corpus (11)

• Fingerprints of spin-orbital entanglement in transition metal oxides
• Spontaneous symmetry breaking in a generalized orbital compass model
• Spin-orbital resonating valence bond liquid on a triangular lattice: Evidence from finite-cluster diagonalization
• Magnetic properties of nanoscale compass-Heisenberg planar clusters
• Entangled spin-orbital phases in the bilayer Kugel-Khomskii model
• Multiflavor Mott insulators in quantum materials and ultracold atoms
• Frustration and Entanglement in Compass and Spin-Orbital Models
• Thermodynamics of symmetric spin--orbital model: One- and two-dimensional cases
• Spin-Orbital Entanglement Emerging from Frustration in the Kugel-Khomskii Model
• Exotic Spin Order due to Orbital Fluctuations
• Spin-Orbital Liquid on a Triangular Lattice