Dicke Phenomena in Condensed Matter*

Recent advances in optical studies of condensed matter systems have led to the emergence of a variety of phenomena that have conventionally been studied in the realm of quantum optics [1]. These studies have not only deepened our understanding of light–matter interactions but also have revealed unique aspects of many-body correlations inherent in condensed matter. This talk will describe our recent studies of cooperative optical processes in solids, fundamentally related to the phenomenon of superradiance, originally predicted by Robert Dicke in 1954 [2]. We have demonstrated that a macroscopic polarization of electron–hole pairs can spontaneously emerge and cooperatively decay, emitting a giant pulse of coherent light, called superfluorescence [3]. We also observed a collective radiative decay of cyclotron resonance of electrons, which led to a decoherence rate that increases linearly with the electron density [4]. Finally, in search of the so-called Dicke superradiant phase transition, we realized collective ultrastrong light–matter coupling in a 2D electron gas in a high-Q terahertz photonic-crystal cavity in a quantizing magnetic field [5,6]. These results show that cooperative effects in solid-state systems are not small corrections that require exotic conditions to be observed; rather, they can dominate the nonequilibrium dynamics and radiative processes of interacting electrons in condensed matter.

1.    K. Cong et al., J. Opt. Soc. Am. B 33, C80 (2016).

2.    R. H. Dicke, Phys. Rev. 93, 99 (1954).

3.    G. T. Noe II et al., Nat. Phys. 8, 219 (2012).

4.    Q. Zhang et al., Phys. Rev. Lett. 113, 047601 (2014).

5.    Q. Zhang et al., Nat. Phys. 12, 1005 (2016).

6.    X. Li et al., Nat. Photon. 12, 324 (2018).