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Quantum-Classical Modeling of Chemical Phenomena

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Boundary treatments of quantum transport in non-equilibrium Greenís function and Wigner distribution methods

Wei Cai

University of N. Carolina, Charlotte


Abstract:   Quantum transport in nano-systems can be modeled using either non-equilibrium Green?s function (NEGF) or Wigner distribution approaches. As the quantum systems are considered open systems, correct boundary conditions are critical for computing the current-voltage characteristics of the systems. Each approach handles the open quantum system in a different manner. The NEGF treats the open boundaries with boundary self-energy defined by a Dirichlet to Neumann mapping, which ensures non-reflection at the device boundaries for electron waves leaving the quantum device active region. On the other hand, the Wigner equation method imposes an inflow boundary treatment [Frensley, 1987] for the Wigner distribution, which in contrast ensures non-reflection at the boundaries for free electron waves entering the device active region. In this talk, we will present recent studies, which clarify the different issues in both boundary treatments such as the size of the contact regions, the various discretizations in the Wigner formulations. Validation for analytical models and resonant tunneling diode (RDT) will be given to assess both types of boundary treatments. (Joint work with Haiyan Jiang)

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