Plasmon Mode Engineering with Electrons on Helium

TL;DR

This paper demonstrates tunable microwave-frequency plasmons in electrons on helium, enabling control over collective charge excitations for potential integration with quantum systems.

Contribution

It introduces a microchannel device that allows precise control and measurement of plasmon modes in electrons on helium, advancing low-dimensional plasmon engineering.

Findings

Plasmon frequencies can be tuned over several GHz by varying electron density.

Power dependence reveals insights into spectral broadening mechanisms.

Electrons on helium serve as versatile platforms for probing collective excitations.

Abstract

An ensemble of electrons trapped above superfluid helium offers a paradigm system for investigating and controlling collective charge dynamics in low-dimensional electronic matter. Of particular interest is the ability to spatially control and engineer surface plasmons for integration with hybrid quantum systems and circuit quantum electrodynamic device architectures. Here we present experiments using an electron-on-helium microchannel device that hosts microwave-frequency plasmons, generated via local microwave excitation in an electrostatically defined central channel. By precisely varying the electron density, we demonstrate tunability of plasmon mode frequencies over several GHz. Additionally, we find that the power dependence of these modes can be used to investigate both homogeneous and inhomogeneous sources of spectral broadening. These results demonstrate the versatility of electrons on helium for probing collective excitations in low-dimensional Coulomb liquids and solids, and demonstrate a path for integrating engineered plasmons in electrons on helium with hybrid circuit quantum electrodynamic systems.