Carpio-Martínez Pablo, Hanna Gabriel
Department of Chemistry, University of Alberta, Edmonton, Alberta T6G 2G2, Canada.
J Chem Phys. 2021 Mar 7;154(9):094108. doi: 10.1063/5.0040752.
Quantum-classical dynamics simulations enable the study of nonequilibrium heat transport in realistic models of molecules coupled to thermal baths. In these simulations, the initial conditions of the bath degrees of freedom are typically sampled from classical distributions. Herein, we investigate the effects of sampling the initial conditions of the thermal baths from quantum and classical distributions on the steady-state heat current in the nonequilibrium spin-boson model-a prototypical model of a single-molecule junction-in different parameter regimes. For a broad range of parameter regimes considered, we find that the steady-state heat currents are ∼1.3-4.5 times larger with the classical bath sampling than with the quantum bath sampling. Using both types of sampling, the steady-state heat currents exhibit turnovers as a function of the bath reorganization energy, with sharper turnovers in the classical case than in the quantum case and different temperature dependencies of the turnover maxima. As the temperature gap between the hot and cold baths increases, we observe an increasing difference in the steady-state heat currents obtained with the classical and quantum bath sampling. In general, as the bath temperatures are increased, the differences between the results of the classical and quantum bath sampling decrease but remain non-negligible at the high bath temperatures. The differences are attributed to the more pronounced temperature dependence of the classical distribution compared to the quantum one. Moreover, we find that the steady-state fluctuation theorem only holds for this model in the Markovian regime when quantum bath sampling is used. Altogether, our results highlight the importance of quantum bath sampling in quantum-classical dynamics simulations of quantum heat transport.
量子 - 经典动力学模拟能够在耦合到热库的分子现实模型中研究非平衡热输运。在这些模拟中，热库自由度的初始条件通常从经典分布中采样。在此，我们研究从量子和经典分布对热库初始条件进行采样，在不同参数区域下，对非平衡自旋 - 玻色子模型（单分子结的典型模型）中稳态热流的影响。对于所考虑的广泛参数区域，我们发现经典热库采样时的稳态热流比量子热库采样时大~1.3 - 4.5倍。使用这两种采样类型时，稳态热流随热库重组能呈现出翻转，经典情况下的翻转比量子情况下更明显，且翻转最大值的温度依赖性不同。随着热库和冷库之间的温度差增加，我们观察到经典和量子热库采样得到的稳态热流差异增大。一般来说，随着热库温度升高，经典和量子热库采样结果之间的差异减小，但在高热库温度下仍不可忽略。这些差异归因于经典分布比量子分布对温度的依赖性更显著。此外，我们发现只有在使用量子热库采样时，稳态涨落定理才适用于该模型在马尔可夫区域的情况。总之，我们的结果突出了量子热库采样在量子热输运的量子 - 经典动力学模拟中的重要性。
