Max-Planck-Institut für Physik komplexer Systeme, 01187 Dresden, Germany.
Phys Rev Lett. 2009 Dec 11;103(24):247001. doi: 10.1103/PhysRevLett.103.247001. Epub 2009 Dec 7.
Excitations which carry "fractional" quantum numbers are known to exist in one dimension in polyacetylene, and in two dimensions, in the fractional quantum Hall effect. Fractional excitations have also been invoked to explain the breakdown of the conventional theory of metals in a wide range of three-dimensional materials. However, the existence of fractional excitations in three dimensions remains highly controversial. In this Letter we report direct numerical evidence for the existence of an extended quantum liquid phase supporting fractional excitations in a concrete, three-dimensional microscopic model-the quantum dimer model on a diamond lattice. We demonstrate explicitly that the energy cost of separating fractional monomer excitations vanishes in this liquid phase, and that its energy spectrum matches that of the Coulomb phase in (3+1)-dimensional quantum electrodynamics.
在一维聚乙炔中已知存在携带“分数”量子数的激发，在二维中存在分数量子霍尔效应。分数激发也被用来解释在广泛的三维材料中常规金属理论的失效。然而，在三维中分数激发的存在仍然存在很大的争议。在这封信中，我们报告了直接的数值证据，证明在一个具体的、三维微观模型——金刚石晶格上的量子二聚体模型中存在扩展的量子液体相，支持分数激发。我们明确地证明了在这个液体相中分离分数单体激发的能量成本消失，并且它的能谱与（3+1）维量子电动力学中的库仑相匹配。
