Ordering and Excitation in Orbital Compass Model on a Checkerboard Lattice
Abstract
We study an orbital compass model on a checkerboard lattice where orbital degree of freedom is represented by the pseudo-spin operator. Competition arises from an Ising interaction for the component of pseudo-spins along the vertical/horizontal bonds and an Ising interaction for the component along diagonal bonds. Classical and quantum compass models are analyzed by utilizing several analytical methods and numerical simulations. At a fully frustrated point where the two Ising interactions compete with each other, a macroscopic number of orbital configurations are degenerate in a classical ground state. This degeneracy is lifted by thermal and quantum fluctuations, and a staggered long-range order of the component of the pseudo-spin is realized. A tricritical point for this order appears due to competition between the bond dependent Ising interactions. Roles of geometrical frustration on excitation dynamics are also examined.
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Cite
@article{arxiv.1203.3683,
title = {Ordering and Excitation in Orbital Compass Model on a Checkerboard Lattice},
author = {Joji Nasu and Synge Todo and Sumio Ishihara},
journal= {arXiv preprint arXiv:1203.3683},
year = {2012}
}
Comments
13 pages, 19 figures