Mixed Quantum-Classical Dynamics of Quantum Energy Transfer Processes

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From predicting new phenomena to interpreting experimental findings, molecular dynamics has become an indispensable tool for both experimentalists and theorists. Adopting a classical description of matter, one can perform molecular dynamics simulations of systems containing very large numbers of particles. However, when particles exhibit wave-like properties, a classical description is no longer valid. Quantum molecular dynamics methods are available, but they are restricted to very small systems as their computational costs scale exponentially with the number of particles. To treat larger systems, one can resort to mixed quantum-classical methods, which treat a key part of the system (i.e., the subsystem) quantum mechanically and the remainder (i.e., the bath) classically. Over the years, a number of mixed quantum-classical dynamics algorithms have been developed. The most accurate of them perform very well, but at high computational costs. Recently, we developed a method that exhibits a favourable balance between computational cost and accuracy. In its present formulation, however, this method is restricted to systems whose potential energies can be expressed in polynomial form and whose subsystems quickly lose memory of the bath dynamics. Thus, the first part of our research program will focus on advancing this methodology along several directions to make it more general, accurate, and efficient. The result promises to be a very powerful tool for simulating the dynamics of mixed quantum-classical systems. The second part of our research program will focus on applying both the present and future formulations of our mixed quantum-classical methodologies to a host of quantum energy transfer/storage processes of fundamental and technological importance. Specifically, we will explore quantum heat transfer processes involved in molecular electronics and nanophononics applications, and energy storage in quantum batteries. Our goals will be to gain an in-depth understanding of the factors that influence the rates/mechanisms of the heat transfer in a variety of molecular systems, and to propose practical designs for quantum batteries. The knowledge gained by this research will ultimately aid in the development of robust, efficient, and controllable nanoscale devices for use in quantum technologies.