High-order multipole radiation from quantum Hall states in Dirac materials
Quantum Hall systems exhibit topologically protected edge states, whose electronic coherence length can achieve a macroscopic spatial extent. In this work, we studied a dramatic consequence of this effect on the optical radiation from such states when this coherence length exceeds the wavelength of light. We find that very high-order multipole radiation is allowed due to the transfer of angular momentum from the edge electron-hole pairs into the emitted light. This effect has not been predicted or observed before and opens up a new perspective on the optical spectroscopy and control of quantum Hall states using multipole radiation.