Nonequilibrium Energy Transport in Nanostructures

随着电子设备和传感设备根据摩尔定律不断变小，出现了几个新的挑战。一方面，量子效应变得占主导地位，必须纳入纳米电路的设计。然而，此外，由于不可避免的欧姆损耗而倾倒的多余能量必须主动地路由出纳米电路，因为被动散热在纳米级失效。由于缺乏足够的理论工具，通过纳米系统的非平衡量子能量传输的主动控制还没有得到广泛的探索。与此同时，量子能量转移对于光合作用中的自然光捕获具有巨大的相关性，光合作用基本上为地球上的生命提供燃料。光合作用开始于生物分子触角复合体对光的吸收。形成激子，然后将其从天线转移到反应中心（RC）。在那里，通过激子的电荷分离启动化学能量储存。这是一个长期存在的难题，大自然如何确保几乎100%的量子产率的能量转移到RC。越来越多的证据表明，长寿命的量子相干是有益的。足够长的生命周期是由于环境波动的相关性，因为它们具有很强的非马尔可夫特性。由于不同的涨落通过非对易算符耦合到激子（位置和耦合能量涨落），因此缺少完整的分析。这将导致强相关动力学的治疗，我们缺乏足够的理论方法。我们的目标是发展一种新的数值方法，通过分子实体和纳米电子器件的能量的非平衡量子输运。它允许描述在不同温度下与几个玻色子能量库接触的驱动量子系统。通过非交换算子耦合到系统的具有任意波动谱的水库将是可处理的。该方法是著名的平衡准绝热路径积分方法的推广。它是基于一个迭代方案，允许计算实验上可访问的观测能量流在一个数值精确的方式。用新的方法，我们将澄清，然后网站和耦合能量波动的相干寿命之间的相关性的影响，更重要的是，对性质优越的上级能量转移效率的光合配合物。此外，我们将确定如何积极有效地控制纳米器件中的量子能量传输，以促进纳米或分子电子学中欧姆损耗的散热。为此，我们研究了扩展的耗散朗道齐纳问题的非平衡和量子控制的能量输运，通过施加激光脉冲。总的来说，我们的方法将允许研究，理解和优化量子能量传输及其在天然和人造纳米结构中的主动控制。

As electronic devices and sensory equipment continuously become smaller following Moore's law several new challenges emerge. On the one hand quantum effects become dominant and have to be included into the design of nanocircuitry. In addition, however, dumped excess energy due to inevitable Ohmic losses has actively to be routed out of the nanocircuit since passive heat sinking fails at the nanoscale. Active control of nonequilibrium quantum energy transport through nanosystems is widely unexplored due to a lack of adequate theoretical tools. Quantum energy transfer, at the same time, is of tremendous relevance for natural light-harvesting in photosynthesis which basically fuels live on earth. Photosynthesis starts with the absorption of light in biomolecular antennae complexes. An exciton is formed which is then transferred from the antenna to a reaction center (RC). There, chemical energy storage is initiated by charge separation of the exciton. It is a long standing puzzle how nature ensures a quantum yield of almost 100 % for the energy transfer to the RC. Growing evidence indicates that long-lived quantum coherence is beneficial. Long enough life times result from correlations in the environmental fluctuations due to their strong non-Markovian character. A full analysis is missing since different fluctuations couple via non-commuting operators to the excitons (site and coupling energy fluctuations). This results in strongly correlated dynamics for whose treatment we lack adequate theoretical methods.Our aim is the development of a novel numerical method for nonequilibrium quantum transport of energy through molecular entities and nanoelectronic devices. It allows to describe driven quantum systems in contact with several bosonic energy reservoirs at different temperatures. Reservoirs with arbitrary fluctuation spectra coupling via non-commuting operators to the system will be treatable. The proposed method is an extension of the well known equilibrium quasi adiabatic path integral approach. It is based on an iterative scheme which allows to calculate experimentally accessible observables as energy current in a numerically exact manner. With the new method we will clarify then the influence of correlations between site and coupling energy fluctuations on coherence life times and, more importantly, on natures superior energy transfer efficiency in hotosynthetic complexes. Furthermore, we will determine how to control actively and efficiently quantum energy transport in nanodevices in order to facilitate heat sinking of Ohmic losses in nano or molecular electronics. To this end we investigate the extension of the dissipative Landau Zener problem to nonequilibrium and quantum control of energy transport by applying laser pulses. In total, our method will allow to study, understand and optimize quantum energy transport and its active control in natural and artificial nanostructures.