Optical dipole orientation of interlayer excitons in MoSe$_{2}$-WSe$_{2}$ heterostacks

Abstract

We report on the far-field photoluminescence intensity distribution of interlayer excitons in MoSe2-WSe2 heterostacks as measured by back focal plane imaging in the temperature range between 1.7 K and 20 K. By comparing the data with an analytical model describing the dipolar emission pattern in a dielectric environment, we are able to obtain the relative contributions of the in-and out-of-plane transition dipole moments associated to the interlayer exciton photon emission. We determine the transition dipole moments for all observed interlayer exciton transitions to be (99 ± 1)% in-plane for R-and H-type stacking, independent of the excitation power and therefore the density of the exciton ensemble in the experimentally examined range. Finally, we discuss the limitations of the presented measurement technique to observe correlation effects in exciton ensembles.

Engineering the radiative dynamics of thermalized excitons with metal interfaces

“…In this case, our model is valid for exciton systems with low oscillator strength, such as interlayer excitons in van der Waals heterostructures, where it is possible to have a high condensed density and avoid strong exciton-exciton annihilation. We note that these interlayer excitons have the same selection rules as 2D TMDCs and have been demonstrated to be 99 ± 1% in-plane [18], corresponding to our in-plane calculations and results.…”

“…In particular, long exciton lifetimes can be achieved in quantum well heterostructures, in which the electron and hole wavefunctions are physically separated, which suppresses radiative recombination and allows for the creation of a thermalized, high density gas [3]. These interlayer systems have the same selection rules as monolayer TMDCs, with circularly polarized, in-plane transitions [17,18]. Recently, these thermalized, high density exciton ensembles have shown experimental signatures of Bose-condensed phases with a non-classical occupation of low momentum states [4,5].…”