Quantum dynamics at the nanoscale

量子动力学在纳米尺度上扮演着极其重要的角色。在纳米尺度上，无论运动是电子的、离子的，还是接近平衡的涨落，动力学都是一个不可避免的因素。当人们希望控制纳米尺度，例如，避免栅电介质的局部失效，通过电子激发来操纵结构，或者在量子信息处理中使用自旋自由度时，动力学过程就会发生。为了在纳米尺度上描述和理解任何过程，平衡结构信息的基本补充是动力学。在化学和材料系统中，原子重排的最终时间标度是单个振动周期(~100ps)。许多重要的现象都起源于在这个时间尺度上发生的过程。为了在纳米尺度上洞察动力学，人们需要一种成熟的一般方法来描述短暂的瞬态态的原子级结构。这一提议的目的是通过耦合薛定谔方程和麦克斯韦方程，使用含时第一性原理框架在纳米尺度上研究电子动力学。这一建议解决了纳米级动力学的理论和量子模拟挑战。这项研究将集中于模拟纳米系统中的非线性动力学，如对飞秒激光脉冲的响应，费米简并电子束的动力学，以及激光激发相干声声子模。这些系统的理论描述和计算模拟是具有挑战性的，因为为了正确地描述电子动力学，人们应该使用具有时变电磁场的含时量子力学方法。在某些情况下，量子核动力学也扮演着重要的角色，人们必须超越Born-Oppenheimer方法。这个提议的目标是提供一个严格的原子论量子力学框架来模拟纳米尺度上的依赖时间的过程。

Quantum dynamics plays an extraordinarily important role at the nanoscale level. Dynamics is an unavoidable ingredient at the nanoscale, whether the movement is electronic, ionic, or a near-equilibrium fluctuation. Dynamical processes occur when one wishes to control the nanoscale, e.g., to avoid local failures of gate dielectrics, to manipulate structures by electronic excitation, or to use the spin degrees of freedom in quantum information processing. To describe and understand any process at the nanoscale level the essential complement to equilibrium structural information is dynamics. The ultimate timescale for atomic rearrangements in chemical and material systems is known to be that of a single vibrational period (~100 fs). Many important phenomena have their origins in processes that occur on this timescale. To get an insight of the dynamics at the nanoscale one needs a well-developed general method for the atomic-level structural description of short-lived transient states. The object of this proposal is to study electron dynamics at the nanoscale using a time-dependent first-principles framework by coupling the Schrodinger and the Maxwell equations. This proposal addresses the theoretical and quantum simulation challenges of nanoscale dynamics. The research will focus on simulating nonlinear dynamics in nanoscale systems, such as response to femtosecond laser pulses, dynamics of Fermi degenerate electron beams, and laser excitation of coherent acoustic phonon modes. The theoretical description and computational simulation of these systems is challenging because for proper description of electron dynamics one should use time-dependent quantum mechanical approach with time-varying electromagnetic fields. In certain cases, the quantum nuclear dynamics also plays important role and one has to go beyond the Born-Oppenheimer approach. The goal of this proposal is to provide a rigorous atomistic quantum mechanical framework to simulate the time-dependent processes at the nanoscale.