Optically Controlled Fluorescence of Floquet Moiré Materials

The optically-induced flat-bands in periodically-driven twisted bilayer graphene (TBG) appear over a range of twist angles away from the magic angle. In this work, we study the drive-controlled optical emission spectrum of TBG driven by a continuous-wave, UV-visible frequency laser. In particular, we find that the steady-state population inversion induced by the laser enables peaks in the optical emission spectrum at terahertz frequencies, originating from electronic transitions between the flat bands of TBG. The amplitude and frequency of the emitted photons are sensitively controlled by the frequency and amplitude of the drive laser and the chiral ratio governing tunneling amplitudes between the layers of TBG. We will discuss the key electron-phonon scattering bottlenecks that enable the downconversion of photon frequency.