Excitation of plasmons in two-dimensional electron gas with defects by microwaves: Wake-field method

TL;DR

This paper presents an analytical wake-field method to study microwave-induced plasmon excitations in a 2D electron gas with defects, highlighting excitation efficiency, wave types, and nonlinear effects.

Contribution

It introduces a novel analytical approach linking wake fields to plasmon excitation, accounting for defect geometry, polarization, and nonlinear phenomena.

Findings

Efficient photon-to-plasmon conversion at specific wave numbers.

Identification of traveling and standing plasmons based on defect geometry.

Nonlinear effects include a frozen charge density wave component.

Abstract

We develop an analytical method to find plasmons generated by microwaves in a two-dimensional electron gas with defects. The excitations are expressed in terms of the wake field of a charged particle moving in plasma. The result explicitly addresses the efficiency of the photon-to-plasmon conversion and the type of excitation. While strong absorption of the radiation by the excitations is reached at larger plasmon wave numbers, intense persistent plasma waves are created at optimal ones. The latter wave numbers depend on the spectrum of plasmons and the distance that the waves are required to travel without being substantially attenuated. Their type, which can be traveling or standing, is governed by the geometry of the defects and the polarization of the radiation. We identify such types of traveling plasmons as circular plasmons, excited at dot defects, and traverse plasmons, excited at straight wire defects and traveling away from (toward) the wires if their group velocity is positive (negative). Nonlinear excitations are also accounted for. In particular, we analyze the zeroth harmonic, linear in the microwave intensity, which has the character of a frozen charge density wave. The interference of elementary wakes from defects arranged in truncated periodic sets can produce amplified plasmons, which are easily portrayed.