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University of Illinois Urbana-Champaign
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Direct determination of momentum-resolved electron transfer in photoexcited mos2/ws2 van der waals heterobilayer
Liu, Fang
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https://hdl.handle.net/2142/107348
Description
Title
Direct determination of momentum-resolved electron transfer in photoexcited mos2/ws2 van der waals heterobilayer
Author(s)
Liu, Fang
Contributor(s)
Zhu, Xiaoyang
Li, Qiuyang
Issue Date
2020-06-25
Keyword(s)
Plenary
Date of Ingest
2020-06-26T03:04:11Z
Abstract
Photo-induced charge separation in transition metal dichalcogenide heterobilayers is being explored for moir\'{e} excitons, spin-valley polarization, and quantum phases of excitons/electrons. While different momentum spaces may be critically involved in charge separation dynamics, little is known directly from experiments. Here we determine momentum-resolved electron dynamics in the \chem{WS_2/MoS_2} heterobilayer using time and angle resolved photoemission spectroscopy (TR-ARPES). Upon photoexcitation in the K valleys, we detect electrons in M/2, M, and Q valleys/points on time scales as short as $\sim$70 fs, followed by dynamic equilibration in K and Q valleys in $\sim$400 fs. The interlayer charge transfer is accompanied by momentum-specific band renormalization. These findings reveal the essential role of phonon scattering, the coexistence of direct and indirect interlayer excitons, and constraints on spin-valley polarization.
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