Master's Defense: Mads Anders Jørgensen

Title: Chiral Berry Plasmons in a Disk

Abstract: Plasmons, collective excitations of free charge carriers, have manifestations in both infinite and bounded systems. The application of an external magnetic field or the use of a material exhibiting non-zero anomalous Hall conductivity allows for a chiral dispersion of the plasmon edge modes in finite systems. For this reason, they are interesting both as an object of study and for their potential application in information transmission. The system of study is that of a two-dimensional disk of charge fluid with a Hall conductance resulting from either a magnetic field or Berry curvature normal to the plane of the disk and with screening plates placed symmetrically above and below the disk-plane. A discretization scheme of modelling the disk as a set of concentric rings is used to numerically solve for the resonant modes and their associated density wave-forms. The resulting dispersions are then compared to those of the infinite half-plane. Screening has a profound effect on the electron interaction and the effect of extreme screening on the dispersions is shown. The dependence of the density wave-forms on angular momentum and excitation is briefly explored. Turning off the free carrier density, akin to setting the chemical potential in the gap of an insulator, is shown numerically to lead to one surviving unidirectional mode.