### 抜粋

We study a doubly degenerate orbital model on a honeycomb lattice. This is a model for orbital states in multiferroic layered iron oxides. The classical and quantum models are analyzed by spin-wave approximation, Monte Carlo simulation, and Lanczos method. A macroscopic number of degeneracy exists in the classical ground state. In the classical model, a peak in the specific heat appears at a temperature which is much lower than the mean-field ordering one. Below this temperature, the angle of orbital pseudospin is fixed, but conventional orbital orders are not suggested. The degeneracy in the ground state is partially lifted by thermal fluctuation. We suggest a role of zero-dimensional fluctuation in hexagons on a low-temperature orbital structure. Lifting of the degeneracy also occurs at zero temperature due to the quantum zero-point fluctuation. We show that the ground-state wave function is well represented by a linear combination of the states where a honeycomb lattice is covered by nearest-neighboring pairs of orbitals with the minimum bond energy.

元の言語 | English |
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記事番号 | 024416 |

ジャーナル | Physical Review B - Condensed Matter and Materials Physics |

巻 | 78 |

発行部数 | 2 |

DOI | |

出版物ステータス | Published - 2008 7 17 |

外部発表 | Yes |

### ASJC Scopus subject areas

- Electronic, Optical and Magnetic Materials
- Condensed Matter Physics

## フィンガープリント Doubly degenerate orbital system in honeycomb lattice: Implication of orbital state in layered iron oxide' の研究トピックを掘り下げます。これらはともに一意のフィンガープリントを構成します。

## これを引用

*Physical Review B - Condensed Matter and Materials Physics*,

*78*(2), [024416]. https://doi.org/10.1103/PhysRevB.78.024416