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Cyclotron resonance in Kondo insulator

Motivated by the recent experimental observations of quantum oscillations in the Kondo insulators SmB$_6$ and YbB$_{12}$, we study magneto-optical conductivity of Kondo insulators. We show that there exist non-trivial cyclotron resonance peaks in a frequency domain below the hybridization gap as a result of the characteristic Landau level structure of the system. Furthermore, these low energy peaks are enhanced near the insulator-metal phase transition driven by an applied magnetic field and stable even at low temperatures. They are smoothly connected via Kondo effect to resonance peaks for unhybridized conduction and $f$-electrons at high temperature. The non-trivial cyclotron resonance is a dynamical counterpart of quantum oscillations in static quantities, and through this intimate connection it will provide a useful insight for the latter.