Graduate students Kubra Eryilmaz and Sina Soleimanikahnoj, former group member Dr. Olafur Jonasson, and Prof. Irena Knezevic coauthored the recent publication “Inflow boundary conditions and nonphysical solutions to the Wigner transport equation” in Journal of Computational Electronics (2021). [Publisher’s link]
Abstract: We investigate the emergence of nonphysical solutions to the steady-state Wigner transport equation on finite-sized simulation domains with inflow boundary conditions. We find that inflow boundary conditions are generally valid, but the wave number uncertainty of injected wave packets has a lower bound that can be significantly higher than usually assumed. Large values of the so-called quantum evolution term (which captures spatial nonlocality in the Wigner transport equation) near simulation-domain boundaries are the cause of spurious reflections, the often-reported discontinuity of the Wigner function at zero wave vector, and negative probabilities. We offer a simple relationship between the lower bound of the wave number uncertainty and simulation parameters that will ensure physical results with inflow boundary conditions.