arXiv subjects

Roelof E. Groenewald

Publications and source records attributed to Roelof E. Groenewald.

2 recordsLinked to original sources

arXiv2021

Impact of Coulomb Scattering on Argon Plasma Based Thermionic Converter Performance

Particle-in-cell (PIC) simulations were performed to study the impact of Coulomb scattering on the performance of argon plasma based thermionic converters. Using a simplified model, studies from the 1970's have concluded that plasma resistance, brought on by Coulomb collisions, causes a shift in the IV-curves of thermionic converters that use an argon plasma to mitigate space charge, thereby strongly limiting their electricity generation capability. In this work the impact of Coulomb collisions in such devices were studied as a function of the relative electrical potential between the electrodes, with higher fidelity through the use of a fully kinetic approach (PIC). This revealed that earlier reports overestimated the negative impact of Coulomb collisions around the flat-band potential. The results of the simulations are also used to comment on the validity of the assumptions made in the simplified model.

physics.plasm-ph↗

arXiv2019

Localized Plasmons in Topological Insulators

We investigate in a fully quantum-mechanical manner how the many-body excitation spectrum of topological insulators is affected by the presence of long-range Coulomb interactions. In the one-dimensional Su-Schrieffer-Heeger model and its mirror-symmetric variant strongly localized plasmonic excitations are observed which originate from topologically non-trivial single-particle states. These \textit{"topological plasmons"} inherit some of the characteristics of their constituent topological single-particle states, but they are not equally well protected against disorder due to the admixture of non-topological bulk single-particle states in the polarization function. The strength of the effective Coulomb interactions is also shown to have strong effects on the plasmonic modes. Furthermore, we show how external modifications via dielectric screening and applied electric fields with distinct symmetries can be used to study topological plasmons, thus allowing for experimental verification of our atomistic predictions.

cond-mat.mtrl-sci↗