Interaction-driven transport of dark excitons in 2D semiconductors with phonon-mediated optical readout

Saroj B. Chand, John M. Woods, Jiamin Quan, Enrique Mejia, Takashi Taniguchi, Kenji Watanabe, Andrea Alù, Gabriele Grosso

Published 2022-12-01Version 1

The growing field of quantum information technology requires propagation of information over long distances with efficient readout mechanisms. Excitonic quantum fluids have emerged as a powerful platform for the realization of such long-range transport due to their straightforward electro-optical conversion. In two-dimensional transition metal dichalcogenides (TMDs), the coupling between spin and valley provides exciting opportunities for harnessing, manipulating and storing bits of information. However, the large inhomogeneity of single layer TMDs cannot be compensated by the weak mutual interaction of bright excitons, hindering spin-valley transport. Nonetheless, the rich band structure of monolayer TMDs supports dark excitonic states with a permanent out-of-plane dipole, strong binding energy and long lifetime, ideally suited to overcome these challenges. Here we show that dark excitons can be used as sturdy information carriers due to their strong interaction that results in diffusion over several micrometers. Experiments conducted in engineered potential energy landscapes show that this repulsion-driven propagation is robust across non-uniform samples including over uphill energy landscapes, and that the information readout is mediated by chiral phonons. The long-range propagation of dark states provides a new concept of excitonic devices for applications in both classical and quantum information technology.