Quantum dynamics at the nanoscale

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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.