Optical Absorption by Indirect Excitons in TMDC Double Layers

We calculate the binding energy, transition energies, oscillator strength, and absorption coefficient of indirect excitons in transition metal dichalcogenide (TMDC) double layers with interstitial few-layer hexagonal boron nitride. The absorption factor, a dimensionless quantity which gives the fraction of incident photons absorbed by each TMDC double layer, is presented and evaluated. The aforementioned optical quantities are obtained for transitions from the ground state to the first two excited states. All quantities were obtained using the solution to the two-body Schrodinger equation for an electron and hole, where the electron-hole interaction is described by the Keldysh potential. For each material, we choose a combination of the exciton reduced mass and the dielectric screening length from the existing literature which give the largest and the smallest indirect exciton binding energy, which provides upper and lower bounds on all quantities presented. Our findings may be verified experimentally, using two-photon spectroscopy to first create the indirect excitons and then probe their excited states.