Prada Adam, Pós Eszter S, Althorpe Stuart C
Yusuf Hamied Department of Chemistry, University of Cambridge, Lensfield Road, Cambridge CB2 1EW, United Kingdom.
J Chem Phys. 2023 Mar 21;158(11):114106. doi: 10.1063/5.0138250.
We report the first numerical calculations in which converged Matsubara dynamics is compared directly with exact quantum dynamics with no artificial damping of the time-correlation functions (TCFs). The system treated is a Morse oscillator coupled to a harmonic bath. We show that, when the system-bath coupling is sufficiently strong, the Matsubara calculations can be converged by explicitly including up to M = 200 Matsubara modes, with the remaining modes included as a harmonic "tail" correction. The resulting Matsubara TCFs are in near-perfect agreement with the exact quantum TCFs, for non-linear as well as linear operators, at a temperature at which the TCFs are dominated by quantum thermal fluctuations. These results provide compelling evidence that incoherent classical dynamics can arise in the condensed phase at temperatures at which the statistics are dominated by quantum (Boltzmann) effects, as a result of smoothing of imaginary-time Feynman paths. The techniques developed here may also lead to efficient methods for benchmarking system-bath dynamics in the overdamped regime.
我们报告了首次数值计算，其中将收敛的松原动力学直接与精确量子动力学进行比较，且不对时间关联函数（TCF）进行人工阻尼。所处理的系统是一个与简谐浴耦合的莫尔斯振子。我们表明，当系统 - 浴耦合足够强时，通过明确包含多达M = 200个松原模式，松原计算可以收敛，其余模式作为简谐“尾部”修正包含在内。在TCF由量子热涨落主导的温度下，对于非线性和线性算符，所得的松原TCF与精确量子TCF几乎完全一致。这些结果提供了令人信服的证据，表明由于虚时费曼路径的平滑，在凝聚相中，当统计由量子（玻尔兹曼）效应主导的温度下，可能会出现非相干经典动力学。这里开发的技术还可能导致在过阻尼 regime 中对系统 - 浴动力学进行基准测试的有效方法。
