Strong coupling of two-dimensional electron ensemble to a single-mode cavity resonator

Abstract

We investigate the regime of strong coupling of an ensemble of two-dimensional electrons to a single-mode cavity resonator. In particular, we realized such a regime of light-matter interaction by coupling the cyclotron motion of a collection of electrons on the surface of liquid helium to the microwave field in a semi-confocal Fabry-Perot resonator. The strong coupling is pronouncedly manifested by the normal-mode splitting in the spectrum of coupled mode-particle motion. Contrary to the usual description of this phenomenon appearing in the recent literature that describes it in terms of quantum electrodynamics (QED), we account for the observed splitting by a model based on classical electrodynamics. We show that the full quantum treatment of this problem results in mean-value equations of motion taht are equivalent to our classical result. This treatment presents a convenient way to describe an ensemble of electrons strongly coupled to a single-mode cavity.