Ultrafast non-excitonic valley Hall effect in MoS<sub>2</sub>/WTe<sub>2</sub> heterobilayers.
basic_science · Level V
Where this comes from
- Record sourced from PubMed, PMID 33712572.
- Also identified by DOI 10.1038/s41467-021-21013-w and PMC identifier 7955044.
- Licence recorded as CC BY.
- The licence permits redistribution, so the abstract is shown in full and the full text is available from the publisher.
Abstract
The valley Hall effect (VHE) in two-dimensional (2D) van der Waals (vdW) crystals is a promising approach to study the valley pseudospin. Most experiments so far have used bound electron-hole pairs (excitons) through local photoexcitation. However, the valley depolarization of such excitons is fast, so that several challenges remain to be resolved. We address this issue by exploiting a unipolar VHE using a heterobilayer made of monolayer MoS<sub>2</sub>/WTe<sub>2</sub> to exhibit a long valley-polarized lifetime due to the absence of electron-hole exchange interaction. The unipolar VHE is manifested by reduced photoluminescence at the MoS<sub>2</sub> A exciton energy. Furthermore, we provide quantitative information on the time-dependent valley Hall dynamics by performing the spatially-resolved ultrafast Kerr-rotation microscopy; we find that the valley-polarized electrons persist for more than 4 nanoseconds and the valley Hall mobility exceeds 4.49 × 10<sup>3</sup> cm<sup>2</sup>/Vs, which is orders of magnitude larger than previous reports.