Electrical Current Injection into Exciton-Polariton Condensates and Polariton-Enhanced Exciton Transport
Year: 2019
Type: dissertation
Abstract: Exciton-polaritons are composite quasiparticles that are the result of coupling excitons with photons. They bring together many of the advantages of both underlying parts: The excitons lend their strong interactions, and the photons give an extremely light mass. Polaritons exist in solid-state systems, which gives them a high potential for device applications, especially as their most interesting quantum effects, Bose-Einstein condensation in particular, become accessible at higher temperatures. In this thesis, I focus primarily on the effects of injecting electrical current into a polariton condensate. I was able to take advantage of the well-established fabrication methods for GaAs-based systems, as well as the high-quality samples developed by my predecessors, which allow the formation of nearly equilibrium condensates over large areas. My colleagues and I then made devices that allow direct injection of electrical charge carriers through polariton condensates in an in-plane direction of the 2D system. I report here three major observations. The first is a superlinear increase in photocurrent, which we attribute to stimulation of an Auger-like scattering of excitons into both the condensate and free carrier states. The second is an increase in the condensate density with current injection, which we explain as stimulated pairing of injected free electrons with intrinsic free holes. The third effect is a shift in the in-plane momentum of polariton condensates with injected current, which is evidence of drag on the polaritons by the free electrons. In addition to the work with electrical current injection, I also report on exciton transport distances in the polariton system. Specifically, very highly excitonic particles are found far from the creation point, with transport distances comparable to those of the much more photonic polaritons. We explain this as an effect of the unusual shape of the polariton energy dispersion.
Author: David Moffat Myers
Language: English
Subfield: Atomic and Molecular Physics, and Optics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: green
OpenAlex ID: W2969455496