Surface and Interface Science Laboratory, RIKEN, Wako, Saitama, 351-0198, Japan.
Department of Physics, University of California San Diego, La Jolla, CA 92093, USA.
Sci Rep. 2017 Aug 29;7(1):9735. doi: 10.1038/s41598-017-09060-0.
Progress in experimental techniques at nanoscale makes measurements of noise in molecular junctions possible. These data are important source of information not accessible through average flux measurements. The emergence of optoelectronics, the recently shown possibility of strong light-matter couplings, and developments in the field of quantum thermodynamics are making measurements of transport statistics even more important. Theoretical methods for noise evaluation in first principles simulations can be roughly divided into approaches for weak intra-system interactions, and those treating strong interactions for systems weakly coupled to baths. We argue that due to structure of its diagrammatic expansion, and the use of many-body states as a basis of its formulation, the recently introduced nonequilibrium diagrammatic technique for Hubbard Green functions is a relatively inexpensive method suitable for evaluation of noise characteristics in first principles simulations over a wide range of parameters. We illustrate viability of the approach by simulations of noise and noise spectrum within generic models for non-, weakly and strongly interacting systems. Results of the simulations are compared to exact data (where available) and to simulations performed within approaches best suited for each of the three parameter regimes.
在纳米尺度的实验技术方面的进展使得对分子结中的噪声进行测量成为可能。这些数据是通过平均通量测量无法获得的重要信息来源。光电技术的出现、最近展示的强物质耦合的可能性以及量子热力学领域的发展，使得传输统计数据的测量变得更加重要。在第一性原理模拟中评估噪声的理论方法大致可以分为处理弱系统内相互作用的方法和处理与浴弱耦合的强相互作用的系统的方法。我们认为，由于其图扩展的结构以及多体态作为其表述基础的使用，最近引入的 Hubbard 格林函数的非平衡图技术是一种相对廉价的方法，适用于在广泛的参数范围内评估第一性原理模拟中的噪声特性。我们通过对非相互作用、弱相互作用和强相互作用系统的通用模型中的噪声和噪声谱的模拟来说明该方法的可行性。模拟结果与精确数据（如有）以及在最适合每个三个参数区域的方法内进行的模拟进行了比较。
