Theory of optical absorption by interlayer excitons in transition metal dichalcogenide heterobilayers

摘要

We present a theory of optical absorption by interlayer excitons in aheterobilayer formed from transition metal dichalcogenides. The theory accountsfor the presence of small relative rotations that produce a momentum shiftbetween electron and hole bands located in different layers, and a moir\'epattern in real space. Because of the momentum shift, the optically activeinterlayer excitons are located at the moir\'e Brillouin zone's corners,instead of at its center, and would have elliptical optical selection rules ifthe individual layers were translationally invariant. We show that the excitonmoir\'e potential energy restores circular optical selection rules by couplingexcitons with different center of mass momenta. A variety of interlayerexcitons with both senses of circular optical activity, and energies that aretunable by twist angle, are present at each valley. The lowest energy excitonstates are generally localized near the exciton potential energy minima. Wediscuss the possibility of using the moir\'e pattern to achieve scalabletwo-dimensional arrays of nearly identical quantum dots.