Max-Plack-Institut für Physik komplexer Systeme, 01187 Dresden, Germany.
J Phys Condens Matter. 2011 Apr 27;23(16):164222. doi: 10.1088/0953-8984/23/16/164222. Epub 2011 Apr 6.
One of the most remarkable examples of emergent quasi-particles is that of the 'fractionalization' of magnetic dipoles in the low energy configurations of materials known as 'spin ice' into free and unconfined magnetic monopoles interacting via Coulomb's 1/r law (Castelnovo et al 2008 Nature 451 42-5). Recent experiments have shown that a Coulomb gas of magnetic charges really does exist at low temperature in these materials and this discovery provides a new perspective on otherwise largely inaccessible phenomenology. In this paper, after a review of the different spin ice models, we present detailed results describing the diffusive dynamics of monopole particles starting both from the dipolar spin ice model and directly from a Coulomb gas within the grand canonical ensemble. The diffusive quasi-particle dynamics of real spin ice materials within the 'quantum tunnelling' regime is modelled with Metropolis dynamics, with the particles constrained to move along an underlying network of oriented paths, which are classical analogues of the Dirac strings connecting pairs of Dirac monopoles.
一个最显著的例子是准粒子的涌现，即在被称为“自旋冰”的材料的低能结构中，磁偶极子的“分数化”成自由和无约束的磁单极子，通过库仑的 1/r 定律相互作用（Castelnovo 等人，2008 年，《自然》451,42-5）。最近的实验表明，在这些材料的低温下，真的存在一个磁荷库仑气体，这一发现为原本难以接近的现象学提供了新的视角。在本文中，在回顾了不同的自旋冰模型之后，我们提出了详细的结果，描述了从偶极自旋冰模型和直接从巨正则系综中的库仑气体出发的磁单极子粒子的扩散动力学。在“量子隧穿”范围内，真实的自旋冰材料的扩散准粒子动力学用 Metropolis 动力学来建模，粒子被约束在沿着一个定向路径的网络上移动，这些路径是连接对 Dirac 磁单极子的 Dirac 弦的经典类比。
