Picosecond Electronic and Structural Dynamics in Photo-excited Monolayer MoSe 2
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MRS Advances © 2018 Materials Research Society DOI: 10.1557/adv.2018.259
Picosecond Electronic and Structural Dynamics in Photo-excited Monolayer MoSe2 Lindsay Bassman1,2,*, Aravind Krishnamoorthy1, Aiichiro Nakano1,2,3,4,5, Rajiv K. Kalia1,2,3,4, Hiroyuki Kumazoe6, Masaaki Misawa6, Fuyuki Shimojo6, Priya Vashishta1,2,3,4 1
Collaboratory for Advanced Computing and Simulations, 2Department of Physics, 3Department of Computer Science 4Department of Chemical Engineering and Material Science, 5Department of Biological Sciences, University of Southern California, Los Angeles, CA 90089, 6Department of Physics, Kumamoto University, Kumamoto 860-8555, Japan
Monolayers of semiconducting transitional metal dichalcogenides (TMDC) are emerging as strong candidate materials for next generation electronic and optoelectronic devices, with applications in field-effect transistors, valleytronics, and photovoltaics. Prior studies have demonstrated strong light-matter interactions in these materials, suggesting optical control of material properties as a promising route for their functionalization. However, the electronic and structural dynamics in response to electronic excitation have not yet been fully elucidated. In this work, we use non-adiabatic quantum molecular dynamics simulations based on time-dependent density functional theory to study lattice dynamics of a model TMDC monolayer of MoSe2 after electronic excitation. The simulation results show rapid, subpicosecond lattice response, as well as finite-size effects. Understanding the sub-picosecond atomic dynamics is important for the realization of optical control of the material properties of monolayer TMDCs, which is a hopeful, straightforward tactic for functionalizing these materials.
INTRODUCTION Monolayers of semiconducting transition metal dichalcogenides (TMDC) are an attractive class of two-dimensional (2D) materials with versatile functionalities that could serve as the next basis for atomic-scale technology1-6. Stable monolayers are relatively straightforward to synthesize from bulk crystals via mechanical or chemical exfoliation due to the weak van der Waals bonding between individual layers7-9. Unique electronic and optoelectronic properties emerge in these monolayers, which are not present in their bulk counterparts. Important examples are strong light-matter interactions10, 11 and tunable semiconducting and metallic structural phases12-14. Together, these qualities make possible ultrafast optical control of structural phase, useful for the formation of defect-free semiconducting-metallic lateral junctions, an essential component in nano-electronics13, 15 and optoelectronics16. Capitalizing on these properties for functional devices requires exquisite control of monolayer systems. Optical control has emerged as a straightforward and clean method, especially where more commonly used methods like chemical doping and mechanical strain fail. However, there is still a great deal to be learned about the sub-picosecond, dynamical response of monolayer TMDCs to pho
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