Microscopic aspects of nonlinearity in condensed matter
Microscopic aspects of nonlinearity in condensed matter
复制标题
凝聚态非线性的微观方面
DOI：
10.1007/978-1-4684-5961-6
复制
发表时间：
1991
期刊：
影响因子：
--
通讯作者：
V. Tognetti
中科院分区：
文献类型：
--
作者：
A. Bishop;V. Pokrovskiǐ;V. Tognetti
我们考虑具有易平面对称的经典二维海森堡模型。kosterlitz和thouless1表明，这样的系统具有拓扑相变：在低温下，存在束缚涡对，在临界温度以上开始解离，在临界温度以上，我们可以假设只有少数自由涡在它们的相互作用之间以弹道方式移动。建立了基于这种“涡旋气体”的动力学模型，假设其速度分布为高斯分布。在这里，我们使用有效的运动方程来表示集体（质心）涡旋变量，并将这些涡旋-涡旋和涡旋-反涡旋相互作用的分析结果与全自旋系统的分子动力学模拟进行比较。我们研究了各向异性参数λ从0到1变化的铁磁体（FM）和反铁磁体（AFM）。
We consider a classical 2D Heisenberg model with easy-plane symmetry. Koster-litz and Thouless1showed that such a system has a topological phase transition: at low temperatures there exist bound vortex pairs which start to dissociate above a critical temperatureTKTJust aboveTKTwe can assume that there are only a few free vortices which move ballistically between their interactions. A model of dynamics built on such a “vortex gas” has been constructed assuming a Gaussian velocity distribution. Here we use effective equations of motion for the collective (center-of-mass) vortex variables and compare these analytical results of vortex-vortex and vortex-anitvortex interactions with molecular dynamics simulations of the full spin system.3We investigate both ferromagnets (FM) and antiferromagnets (AFM) with an anisotropy parameter λ varying from zero to one.