Coupled pair of one and two dimensional magneto-plasmons on electrons on helium

TL;DR

This paper investigates coupled one- and two-dimensional magneto-plasmons on electrons on helium, revealing a delocalized bulk mode induced by a density gradient and its interaction with edge modes, with experimental confirmation.

Contribution

It introduces a theoretical and experimental study of a delocalized magneto-plasmon mode caused by density gradients, coexisting with edge modes on electrons on helium.

Findings

Identification of a delocalized magneto-plasmon mode via resonance measurements.

Experimental confirmation of mode existence through admittance spectra.

Potential implications for understanding topological material transport.

Abstract

Electrons on the liquid helium surface form an extremely clean two dimensional system where different plasmon-excitations can coexist. Under a magnetic field time reversal symmetry is broken and all the bulk magneto-plasmons become gaped at frequencies below cyclotron resonance while chiral one dimensional edge magneto-plasmons appear at the system perimeter. We theoretically show that the presence of a homogeneous density gradient in the electron gas leads to the formation of a delocalized magneto-plasmon mode in the same frequency range as the lowest frequency edge-magnetoplasmon mode. We experimentally confirm its existence by measuring the corresponding resonance peak in frequency dependence of the admittance of the electron gas. This allows to realize a prototype system to investigate the coupling between a chiral one-dimensional mode and a single delocalized bulk mode. Such a model system can be important for the understanding of transport properties of topological materials where states of different dimensionality can coexist.