Isakov S V, Moessner R, Sondhi S L
Department of Physics, University of Toronto, Toronto, Ontario M5S 1A7, Canada.
Phys Rev Lett. 2005 Nov 18;95(21):217201. doi: 10.1103/PhysRevLett.95.217201. Epub 2005 Nov 14.
The low-temperature entropy of the spin ice compounds, such as and , is well described by the nearest-neighbor antiferromagnetic Ising model on the pyrochlore lattice, i.e., by the "ice rules." This is surprising since the dominant coupling between the spins is their long ranged dipole interaction. We show that this phenomenon can be understood rather elegantly: one can construct a model dipole interaction, by adding terms of shorter range, which yields precisely the same ground states, and hence entropy, as the nearest-neighbor interaction. A treatment of the small difference between the model and true dipole interactions reproduces the numerical work by Gingras et al. in detail. We are also led to a more general concept of projective equivalence between interactions.
诸如[具体化合物1]和[具体化合物2]等自旋冰化合物的低温熵，由烧绿石晶格上的近邻反铁磁伊辛模型很好地描述，即由“冰规则”描述。这很令人惊讶，因为自旋之间的主导耦合是它们的长程偶极相互作用。我们表明，这种现象可以相当巧妙地理解：通过添加短程项，可以构建一个模型偶极相互作用，它产生与近邻相互作用完全相同的基态，从而产生相同的熵。对模型和真实偶极相互作用之间的微小差异进行处理，详细再现了金格拉斯等人的数值研究结果。我们还引出了相互作用之间射影等价的更一般概念。
