Negative circular polarization emissions from WSe2/MoSe2 commensurate heterobilayers

Horng-Tay Jeng,Wen-Hao Chang,Po-Hsun Wu,Lain-Jong Li,Pei-Ying Wu,Ming-Hao Lee,Li-Syuan Lu,Yi-Chia Chou,Wei-Ting Hsu,Ming-Wen Chu,Peng-Jen Chen

doi:10.1038/s41467-018-03869-7

Abstract

Van der Waals heterobilayers of transition metal dichalcogenides with spin–valley coupling of carriers in different layers have emerged as a new platform for exploring spin/valleytronic applications. The interlayer coupling was predicted to exhibit subtle changes with the interlayer atomic registry. Manually stacked heterobilayers, however, are incommensurate with the inevitable interlayer twist and/or lattice mismatch, where the properties associated with atomic registry are difficult to access by optical means. Here, we unveil the distinct polarization properties of valley-specific interlayer excitons using epitaxially grown, commensurate WSe2/MoSe2 heterobilayers with well-defined (AA and AB) atomic registry. We observe circularly polarized photoluminescence from interlayer excitons, but with a helicity opposite to the optical excitation. The negative circular polarization arises from the quantum interference imposed by interlayer atomic registry, giving rise to distinct polarization selection rules for interlayer excitons. Using selective excitation schemes, we demonstrate the optical addressability for interlayer excitons with different valley configurations and polarization helicities.

Highlights

Van der Waals heterobilayers of transition metal dichalcogenides with spin–valley coupling of carriers in different layers have emerged as a new platform for exploring spin/valleytronic applications
Manually stacked hBLs are generally incommensurate with inevitable interlayer twist and/or lattice mismatch, which could lead to a periodic variation of the atomic registry between individual monolayers, i.e., the so-called Moiré superlattice[19, 20]
We address how the interlayer atomic registry impacts the optical transition and polarization properties of interlayer excitons by using commensurate WSe2/monolayer WSe2 (MoSe2) hBLs formed by direct growth using chemical vapor deposition (CVD)

Summary

Introduction

Van der Waals heterobilayers of transition metal dichalcogenides with spin–valley coupling of carriers in different layers have emerged as a new platform for exploring spin/valleytronic applications. We address how the interlayer atomic registry impacts the optical transition and polarization properties of interlayer excitons by using commensurate WSe2/MoSe2 hBLs formed by direct growth using chemical vapor deposition (CVD). The impacts of stacking order on the formation processes of bright interlayer exciton states with different valley configurations are discussed.

Results

Conclusion