Valence Bond Crystal and possible orbital pinball liquid in a t2g model

Abstract

We study a model for orbitally degenerate Mott insulators, where localized electrons possess t_2g degrees of freedom coupled by several, competing, exchange mechanisms. We provide evidence for two distinct strongly fluctuating regimes, depending on whether superexchange or direct exchange mechanism predominates. In the superexchange-dominated regime, the ground state is dimerized, with nearest neighbor orbital singlets covering the lattice. By deriving an effective quantum dimer model and analyzing it numerically, we characterize this dimerized phase as a valence bond crystal stabilized by singlet resonances within a large unit cell. In the opposite regime, with predominant direct exchange, the combined analysis of the original model and another effective model adapted to the local constraints, shows that subleading perturbations select a highly resonating ground state, with coexisting diagonal and off-diagonal long-range orbital orders.

14 pages, 13 figures

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Cited by in corpus (13)

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• Combined topological and Landau order from strong correlations in Chern bands
• Variational tensor network renormalization in imaginary time: Two-dimensional quantum compass model at finite temperature
• Exotic spin orders driven by orbital fluctuations in the Kugel-Khomskii model
• Quantum phase transitions in exactly solvable one-dimensional compass models
• Phase diagram of the 1/3-filled extended Hubbard model on the Kagome lattice
• Symmetry properties and spectra of the two-dimensional quantum compass model
• Resonating valence bond physics is not always governed by the shortest tunneling loops
• Role of the spin-orbit coupling in the Kugel-Khomskii model on the honeycomb lattice
• Mechanism of hole propagation in the orbital compass models
• Locally tunable disorder and entanglement in the one-dimensional plaquette orbital model
• Particle-Hole Asymmetry and Pinball Liquid in a Triangular-Lattice Extended Hubbard Model within Mean-Field Approximation
• One-dimensional frustrated plaquette compass model: Nematic phase and spontaneous multimerization