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.

https://arxiv.org/abs/1701.03464

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