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arXiv 0905.2261quant-ph
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耗散系统中线形的主方程方法

Master equation approach to line shape in dissipative systems

Chikako Uchiyama, Masaki Aihara, Mizuhiko Saeki, Seiji Miyashita

摘要:

我们提出了一个配方,以获得线形状的磁响应与耗散效应,直接反映了环境的性质。利用响应函数的时间演化与约化密度算符的时间演化相同的事实,我们给出了复磁化率的完整描述。我们使用约化密度算子的运动方程描述动力学,包括系统和热浴之间的初始相关项。在这种形式主义中,我们对待非马尔可夫动力学的完整描述,包括初始相关性。我们提出了一个明确的和紧凑的公式,直到二阶累积量,它可以直接应用于多自旋系统。我们还考虑了系统浴相互作用的频率偏移。我们研究的依赖关系的线的形状上的类型的系统和热浴之间的相互作用。我们证明,目前的形式主义是一个强大的工具,用于调查各种系统,我们展示了它是如何适用于自旋系统,包括那些多达三个自旋。我们区分了初始关联和频移的贡献,明确了它们在欧姆耦合谱函数中的作用。作为多自旋系统的应用程序的例子,我们得到的线形的依赖关系的空间取向的方向的静态场(永田的影响),包括热环境的影响,在一个双自旋系统,随着依赖关系的安排在一个三自旋系统的三角形。

英文摘要:

We propose a formulation to obtain the line shape of a magnetic response with dissipative effects that directly reflects the nature of the environment. Making use of the fact that the time evolution of a response function is described by the same equation as the reduced density operator, we formulate a full description of the complex susceptibility. We describe the dynamics using the equation of motion for the reduced density operator, including the term for the initial correlation between the system and a thermal bath. In this formalism, we treat the full description of non-Markovian dynamics, including the initial correlation. We present an explicit and compact formula up to the second order of cumulants, which can be applied in a straightforward way to multiple spin systems. We also take into account the frequency shift by the system-bath interaction. We study the dependence of the line shape on the type of interaction between the system and the thermal bath. We demonstrate that the present formalism is a powerful tool for investigating various kinds of systems, and we show how it is applied to spin systems, including those with up to three spins. We distinguish the contributions of the initial correlation and the frequency shift, and make clear the role of each contribution in the Ohmic coupling spectral function. As examples of applications to multispin systems, we obtain the dependence of the line shape on the spatial orientation in relation to the direction of the static field (Nagata-Tazuke effect), including the effects of the thermal environment, in a two-spin system, along with the dependence on the arrangement of a triangle in a three-spin system.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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