title: The role of collective motion in the ultrafast charge transfer in van der Waals heterostructures.
abstract: The success of van der Waals heterostructures made of graphene, metal dichalcogenides and other layered materials, hinges on the understanding of charge transfer across the interface as the foundation for new device concepts and applications. In contrast to conventional heterostructures, where a strong interfacial coupling is essential to charge transfer, recent experimental findings indicate that van der Waals heterostructues can exhibit ultrafast charge transfer despite the weak binding of these heterostructures. Here we find, using time-dependent density functional theory molecular dynamics, that the collective motion of excitons at the interface leads to plasma oscillations associated with optical excitation. By constructing a simple model of the van der Waals heterostructure, we show that there exists an unexpected criticality of the oscillations, yielding rapid charge transfer across the interface. Application to the MoS2/WS2 heterostructure yields good agreement with experiments, indicating near complete charge transfer within a timescale of 100 fs.
authors.affiliation: Department of Physics, Applied Physics, and Astronomy, Rensselaer Polytechnic Institute, Troy, New York 12180, USA.
authors.forename: Han
authors.identifier: 0000-0002-7476-6012
authors.initials: H
authors.lastname: Wang
authors.affiliation: Spin Engineering Physics Team, Korea Basic Science Institute (KBSI), Daejeon 305-806, Korea.
authors.forename: Junhyeok
authors.initials: J
authors.lastname: Bang
authors.affiliation: Department of Physics, Applied Physics, and Astronomy, Rensselaer Polytechnic Institute, Troy, New York 12180, USA.
authors.forename: Yiyang
authors.initials: Y
authors.lastname: Sun
authors.affiliation: Department of Physics, Applied Physics, and Astronomy, Rensselaer Polytechnic Institute, Troy, New York 12180, USA.|Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA.
authors.forename: Liangbo
authors.identifier: 0000-0003-1199-0049
authors.initials: L
authors.lastname: Liang
authors.affiliation: Department of Physics, Applied Physics, and Astronomy, Rensselaer Polytechnic Institute, Troy, New York 12180, USA.
authors.forename: Damien
authors.initials: D
authors.lastname: West
authors.affiliation: Department of Physics, Applied Physics, and Astronomy, Rensselaer Polytechnic Institute, Troy, New York 12180, USA.
authors.forename: Vincent
authors.initials: V
authors.lastname: Meunier
authors.affiliation: Department of Physics, Applied Physics, and Astronomy, Rensselaer Polytechnic Institute, Troy, New York 12180, USA.
authors.forename: Shengbai
authors.initials: S
authors.lastname: Zhang