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Nano Lett. 2017 Dec 13;17(12):7761-7766. doi: 10.1021/acs.nanolett.7b03955. Epub 2017 Nov 15.

Dynamic Optical Tuning of Interlayer Interactions in the Transition Metal Dichalcogenides.

Author information

1
Department of Materials Science and Engineering, Stanford University , Stanford, California 94305, United States.
2
Department of Chemistry, Stanford University , Stanford, California 94305, United States.
3
Department of Applied Physics, Stanford University , Stanford, California 94305, United States.
4
PULSE Institute, SLAC National Accelerator Laboratory , Menlo Park, California 94025, United States.
5
Department of Physics, University of Texas, Austin , Austin, Texas 78712, United States.
6
Stanford Institute for Materials and Energy Sciences, SLAC National Accelerator Laboratory , Menlo Park, California 94025, United States.
7
Department of Physics, Wesleyan University , Middleton, Connecticut 06459, United States.
8
Advanced Photon Source, Argonne National Laboratory , Argonne, Illinois 60439, United States.
9
Department of Physics, University of Washington , Seattle, Washington 98195, United States.
10
Department of Geological Sciences, Stanford University , Stanford, California 94305, United States.
11
SLAC National Accelerator Laboratory , Menlo Park, California 94025, United States.
12
Department of Materials Science and Engineering, North Carolina State University , Raleigh, North Carolina 27695, United States.
13
School for Engineering of Matter, Transport, and Energy, Arizona State University , Tempe, Arizona 85287, United States.
14
Department of Chemistry, Columbia University , New York, New York 10027, United States.
15
Department of Physics and Astronomy, University of Missouri , Columbia, Missouri 65211-7010, United States.

Abstract

Modulation of weak interlayer interactions between quasi-two-dimensional atomic planes in the transition metal dichalcogenides (TMDCs) provides avenues for tuning their functional properties. Here we show that above-gap optical excitation in the TMDCs leads to an unexpected large-amplitude, ultrafast compressive force between the two-dimensional layers, as probed by in situ measurements of the atomic layer spacing at femtosecond time resolution. We show that this compressive response arises from a dynamic modulation of the interlayer van der Waals interaction and that this represents the dominant light-induced stress at low excitation densities. A simple analytic model predicts the magnitude and carrier density dependence of the measured strains. This work establishes a new method for dynamic, nonequilibrium tuning of correlation-driven dispersive interactions and of the optomechanical functionality of TMDC quasi-two-dimensional materials.

KEYWORDS:

2D materials; Casimir effect; femtosecond X-ray scattering; interlayer van der Waals interactions; ultrafast

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