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arXiv · 1105.5757

Trimer Formation and Metal-Insulator Transition in Orbital Degenerate Systems on a Triangular Lattice

Junki Yoshitake·Yukitoshi Motome
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Abstract

As a prototypical self-organization in the system with orbital degeneracy, we theoretically investigate trimer formation on a triangular lattice, as observed in LiVO2. From the analysis of an effective spin-orbital coupled model in the strong correlation limit, we show that the previously-proposed orbital-ordered trimer state is not the lowest-energy state for a finite Hund's-rule coupling. Instead, exploring the ground state in a wide range of parameters for a multiorbital Hubbard model, we find an instability toward a different orbital-ordered trimer state in the intermediately correlated regime in the presence of trigonal crystal field. The trimer phase appears in the competing region among a paramagnetic metal, band insulator, and Mott insulator. The underlying mechanism is nesting instability of the Fermi surface by a synergetic effect of Coulomb interactions and trigonal-field splitting. The results are compared with experiments in triangularlattice compounds, LiVX2 (X=O, S, Se) and NaVO2.

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Junki Yoshitake, Yukitoshi Motome. 2011-05-29. Trimer Formation and Metal-Insulator Transition in Orbital Degenerate Systems on a Triangular Lattice. https://doi.org/10.1143/jpsj.80.073711

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