Superradiant Decay of Cyclotron Resonance of Two-Dimensional Electron Gases

TL;DR

This paper demonstrates superradiant decay of cyclotron resonance in high-mobility 2D electron gases, showing a linear relationship between decay rate and electron density, supported by quantum theory and experimental data.

Contribution

It provides the first experimental observation and theoretical explanation of superradiant damping in cyclotron resonance of 2D electron gases.

Findings

Decay rate increases linearly with electron density.

Quantum theory accurately predicts decay rates.

CR decoherence is many-body in nature despite Kohn's theorem.

Abstract

We report on the observation of collective radiative decay, or superradiance, of cyclotron resonance (CR) in high-mobility two-dimensional electron gases in GaAs quantum wells using time-domain terahertz magnetospectroscopy. The decay rate of coherent CR oscillations increases linearly with the electron density in a wide range, which is a hallmark of superradiant damping. Our fully quantum mechanical theory provides a universal formula for the decay rate, which reproduces our experimental data without any adjustable parameter. These results firmly establish the many-body nature of CR decoherence in this system, despite the fact that the CR frequency is immune to electron-electron interactions due to Kohn's theorem.