ArticleZhang Q, Arikawa T, Kato E, Reno JL, Pan W, Watson JD, Manfra MJ, Zudov MA, Tokman M, Erukhimova M, Belyanin A, Kono J.
Phys Rev Lett. 2014 Jul 25;113(4):047601.
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.