Propagation of excitons in TMDC monolayers with suppressed disorder

Coulomb-bound electron-hole pairs, or excitons, dominate the electro-optical properties in single layers of semiconducting transition metal dichalcogenides (TMDCs) and their heterostructures. In these 2D systems, excitons can move freely across large distances¹. We study exciton propagation by directly monitoring their spatial behavior in single layers of TMDCs by spatially- and time-resolved photoluminescence microscopy². In high-quality boron nitride encapsulated samples with strongly suppressed disorder³ we find very efficient diffusion at low excitation densities and a strongly non-linear behavior at high densities. Single layers of encapsulated TMDCs provide a highly promising platform to explore exciton transport phenomena, including low-temperature conditions with suppressed phonon-scattering and manipulation of spin-valley polarized excitations.

¹ N. Kumar, Q. Cui, F. Ceballos, D. He, Y. Wang and H. Zhao, Phys. Rev. B 89, 125427 (2014).
² M. Kulig, J. Zipfel, P. Nagler, S. Blanter, C. Sch�uller, T. Korn, N. Paradiso, M.M. Glazov and A. Chernikov, Phys. Rev. Lett. 120, 207401 (2018).
³ A. Raja, L. Waldecker, J. Zipfel, Y. Cho, S. Brem, J.D. Ziegler, M. Kulig, T. Tanaguchi, K. Watanabe, E. Malic, T.F. Heinz, T.C. Berkelbach and A. Chernikov, Nat. Nanotech. 14, 832-837 (2019).