Chiral terahertz photocurrent in quantum point contact–split ring resonator coupled systems in the quantum Hall regime

Light-matter interaction between cyclotron resonance and photons in a plasmonic resonator enables the formation of polaritons in the ultrastrong coupling regime. While optical studies are common, the authors demonstrate here electrical detection of ultrastrong coupling via terahertz-induced photocurrent through a quantum point contact and reveal the chiral behavior of the photocurrent with respect to magnetic field. Their theoretical model based on nonequilibrium electron distribution in edge channels agrees well with the experimental data, which offers new insights into light-matter interactions.