热噪声和关联噪声对量子铁磁体中磁振子的影响
The effects of thermal and correlated noise on magnons in a quantum ferromagnet
摘要：
研究了量子铁磁体中自旋波（磁振子）的动力学和热平衡以及宏观磁化强度。热噪声，由于与晶格声子的相互作用和空间相关性的噪声的影响被认为是。首先，我们提出了一个马尔可夫主方程的方法与分析解决方案的任何齐次空间关联函数的噪声。我们发现，空间相关的噪声增加的衰减率的低波矢量的磁振子的热平衡，这也导致了更快的衰减的铁磁体的磁化强度的稳态值。对于长的相关长度和较高的温度，我们发现，另外有一个组件的磁化衰减非常缓慢，由于快速磁振子的衰减率降低。这种效应可能对快速和噪声保护的量子或经典信息传输和磁振子有用。我们进一步比较铁磁和反铁磁的行为在嘈杂的环境中，并找到定性类似的行为欧姆，但从根本上不同的行为在超欧姆环境。
英文摘要：
The dynamics and thermal equilibrium of spin waves (magnons) in a quantum ferromagnet as well as the macroscopic magnetisation are investigated. Thermal noise due to an interaction with lattice phonons and the effects of spatial correlations in the noise are considered. We first present a Markovian master equation approach with analytical solutions for any homogeneous spatial correlation function of the noise. We find that spatially correlated noise increases the decay rate of magnons with low wave vectors to their thermal equilibrium, which also leads to a faster decay of the ferromagnet's magnetisation to its steady-state value. For long correlation lengths and higher temperature we find that additionally there is a component of the magnetisation which decays very slowly, due to a reduced decay rate of fast magnons. This effect could be useful for fast and noise-protected quantum or classical information transfer and magnonics. We further compare ferromagnetic and antiferromagnetic behaviour in noisy environments and find qualitatively similar behaviour in Ohmic but fundamentally different behaviour in super-Ohmic environments.
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