Twist-angle-dependent momentum-space direct and indirect interlayer excitons in WSe₂/WS₂ heterostructure

Abstract

Under specific twist angles, the regulation of direct (indirect) interlayer excitons is realized by applying an external electric field.

Ultrafast Interlayer Charge Transfer Outcompeting Intralayer Valley Relaxation in Few-Layer 2D Heterostructures

“…As schematically illustrated in Figure d, after photoexciting an intralayer exciton at the K valley of the WSe 2 monolayer, an electron transfers from K c of WSe 2 to that of the WS 2 layer, forming a long-lived interlayer exciton. Previous electronic structure calculation on WSe 2 /WS 2 1L_HS has shown the conduction band at the Q valley is hybridized with contributions from both WSe 2 and WS 2 and lies in-between K c of WSe 2 and WS 2 . − In 1L_HS here, we cannot differentiate whether an electron in K c of WSe 2 transfers directly to K c of WS 2 or is mediated by Q c since TA spectroscopy lacks momentum information. We also performed the same measurements on 2L_WSe 2 /WS 2 HS (2L_HS) and observed similarly ultrafast (<50 fs) electron transfer from photoexcited 2L_WSe 2 to WS 2 , forming a long-lived interlayer charge separation (Figure S2).…”

Electrically tunable non-radiative lifetime in WS2/WSe2 heterostructures

“…3a, the heterostructure sample does not exhibit PL emission from interlayer exciton, due to the large twist-angle induced momentum mismatch. 34,35 We therefore focused our investigation on intralayer exciton resonances in the WS 2 /WSe 2 heterostructure. TRPL measurements were carried out using a 10 ps excitation laser at a wavelength of 532 nm (∼2.33 eV).…”

Revealing the Optical Transition Properties of Interlayer Excitons in Defective WS2/WSe2 Heterobilayers

“…In 2020, Zeng et al reported that multiple emission sources of defect-bound excitons in the PL spectra of twisted bilayer WSe 2 originate from different defect sites within the material . Sometimes, defect-trapped exciton and interlayer excitons in heterobilayers exhibit close proximity in terms of energy and peak line shape, requiring researchers to conduct extensive studies for differentiation between the defect-trapped exciton and interlayer exciton. , For the MoSe 2 /WSe 2 heterobilayers, the broad shoulders below the IX PL in emission spectra are typically attributed to the defect-trapped exciton, as these peaks saturate rapidly under high laser power and quench at higher temperatures. , The peak shift and broadening of interlayer excitons in a MoS 2 /WSe 2 heterobilayer are believed to be correlated to the defects and impurities . It is evident that defects have a significant effect on the optical properties of interlayer excitons in twisted TMDs.…”