Segal Dvira
Chemical Physics Theory Group, Department of Chemistry, University of Toronto, 80 Saint George St., Toronto, Ontario M5S 3H6, Canada.
J Chem Phys. 2014 Apr 28;140(16):164110. doi: 10.1063/1.4871874.
We study the non-adiabatic dynamics of a two-state subsystem in a bath of independent spins using the non-interacting blip approximation, and derive an exact analytic expression for the relevant memory kernel. We show that in the thermodynamic limit, when the subsystem-bath coupling is diluted (uniformly) over many (infinite) degrees of freedom, our expression reduces to known results, corresponding to the harmonic bath with an effective, temperature-dependent, spectral density function. We then proceed and study the heat current characteristics in the out-of-equilibrium spin-spin-bath model, with a two-state subsystem bridging two thermal spin-baths of different temperatures. We compare the behavior of this model to the case of a spin connecting boson baths, and demonstrate pronounced qualitative differences between the two models. Specifically, we focus on the development of the thermal diode effect, and show that the spin-spin-bath model cannot support it at weak (subsystem-bath) coupling, while in the intermediate-strong coupling regime its rectifying performance outplays the spin-boson model.
我们使用非相互作用脉冲近似研究了处于独立自旋浴中的两态子系统的非绝热动力学，并推导了相关记忆核的精确解析表达式。我们表明，在热力学极限下，当子系统 - 浴耦合在许多（无限）自由度上被（均匀地）稀释时，我们的表达式简化为已知结果，对应于具有有效、温度相关谱密度函数的谐振浴。然后我们继续研究非平衡自旋 - 自旋 - 浴模型中的热流特性，其中一个两态子系统连接两个不同温度的热自旋浴。我们将该模型的行为与自旋连接玻色子浴的情况进行比较，并展示了这两个模型之间明显的定性差异。具体而言，我们关注热二极管效应的发展，并表明自旋 - 自旋 - 浴模型在弱（子系统 - 浴）耦合下无法支持该效应，而在中强耦合 regime 中其整流性能优于自旋 - 玻色子模型。
