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Orbital liquid in three dimensional Mott insulator: $LaTiO_3$

G. Khaliullin·S. Maekawa
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Abstract

We present a theory of spin and orbital states in Mott insulator $LaTiO_3$. The spin-orbital superexchange interaction between $d^1(t_{2g})$ ions in cubic crystal suffers from a pathological degeneracy of orbital states at classical level. Quantum effects remove this degeneracy and result in the formation of the coherent ground state, in which the orbital moment of $t_{2g}$ level is fully quenched. We find a finite gap for orbital excitations. Such a disordered state of local degrees of freedom on unfrustrated, simple cubic lattice is highly unusual. Orbital liquid state naturally explains observed anomalies of $LaTiO_3$.

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G. Khaliullin, S. Maekawa. 2000-08-02. Orbital liquid in three dimensional Mott insulator: $LaTiO_3$. https://doi.org/10.1103/physrevlett.85.3950

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