Nonequilibrium Charge Transport in Molecular Nanostructures: Theory and Applications

近年来，对分子纳米结构中量子输运过程的研究和理解受到了极大的关注。在所研究的各种过程和结构中，分子结（即结合到金属或半导体电极的单分子）中的电荷和能量传输特别令人感兴趣。这些系统结合了联合收割机的可能性，在纳米尺度上研究非平衡多体量子物理学的基本方面与纳米电子器件技术应用的前景。虽然已经获得了一个基本的了解，在分子结的稳态传输特性，这是不是在这些系统中的非平衡条件下的瞬态和时间依赖性的现象的情况下。本提案的目的是发展理论方法，允许在分子纳米结构中的非平衡输运过程的准确和有效的描述，并应用这些方法来阐明基本的物理机制。要研究的方面包括稳定状态的存在性和唯一性，在分子结，时间尺度和动力学的方法，稳定状态，有关的电子-电子和电子振动相互作用，开关和滞后的松弛机制的重要性，以及可能性，以控制特定的量子状态下的非平衡条件下的路径。此外，波动和噪声现象将在该项目中进行研究。这些方面都将研究通用模型，以及为具体的例子，分子结的基础上的第一原理描述。该项目的长期目标是全面了解非平衡条件下分子纳米结构中传输过程中的瞬态和时间依赖性现象。

The study and understanding of quantum transport processes in molecular nanostructures has received great attention recently. Among the variety of processes and architectures investigated, charge and energy transport in molecular junctions, i.e. single molecules bound to metal or semiconductor electrodes, have been of particular interest. These systems combine the possibility to study fundamental aspects of nonequilibrium many-body quantum physics at the nanoscale with the perspective for technological applications in nanoelectronic devices. While a basic understanding of steady state transport properties in molecular junctions has been obtained, this is not the case for transient and time-dependent phenomena in these systems under nonequilibrium conditions. The objective of this proposal is to develop theoretical methods that allow an accurate and efficient description of nonequililbrium transport processes in molecular nanostructures and apply these methods to elucidate the fundamental physical mechanisms. Aspects to be investigated include the existence and uniqueness of steady states in molecular junctions, time scales and dynamics of approach to steady state, importance of relaxation mechanisms related to electron-electron and electron-vibrational interaction, switching and hysteresis, as well as possibilities to control pathways to specific quantum states under nonequilibrium conditions. Furthermore, fluctuation and noise phenomena will be investigated in the project. These aspects will be studied both for generic models as well as for specific examples of molecular junctions based on a first principles description. The long-term goal of this project is to obtain a comprehensive understanding of transient and time-dependent phenomena in transport processes in molecular nanostructures under nonequilibrium conditions.