Report

Teaser, summary, work performed and final results

Periodic Reporting for period 1 - MODHET (Modelling 2D Transition Metal Dichalcogenide Heterostructures)

Teaser

The availability of stable atomic thin layers of 2D crystal enable the realization of van der Waals materials by stacking different layer materials together. The studies of 2D van der Waals materials will significantly expand the field of 2D materials and eventually lead to...

Summary

The availability of stable atomic thin layers of 2D crystal enable the realization of van der Waals materials by stacking different layer materials together. The studies of 2D van der Waals materials will significantly expand the field of 2D materials and eventually lead to new development of condense matter physics and next generation of 2D electronic device applications. The quantum engineering in these artificial structures and architectures with desired and tailored properties requires microscopic understanding of the physical properties of 2D crystals and the interaction between them, which is the issue being addressed in this project. Nevertheless, these studies contains many aspects and developing rapidly. The overall objective of this project is focus on studying the electronic and plasmonic properties and electron-electron correlations in van der Waals 2D materials, in particular, the 2D TMD heterostructures.

Work performed

\"We performed the first principles calculations to study the band structures and plasmonic properties of 2D heterostructures with different combinations. Based on these results, we further proposed a general model for the plasmon dispersion in quasi-2D metals and confirmed it with ab initio calculations. In addition, we investigated the structure of stanene grown on Ag(111) surface, and explored the novel structures for group VI elemental 2D materials with DFT calculations. Moreover, utilizing our knowledge on 2D TMDs, we studied the absorption and charge transfer of different gas molecules on 2D WS2 with DFT calculations. Finally, we investigate the modulations of electronic band structures and electron-electron correlations in twisted bilayer systems, in particular, the twisted bilayer hBN.
The main results obtained this project includes:

•2D TMD plasmonics: understanding how plasmons can be tuned in 2D TMD heterstructures, obtaining a general model for plasmon dispersions in quasi-2D matals, and predicting the long-lived and highly-localized plasmons in quasi-2D metals for large wavevectors.

•Novel 2D materials:
oStanene: Identifying the structure of monolayer stanene grown on the Ag(111) surface and confirming the growth of large area stanene layers on the Ag(111) surface.
oSelenene and tellurene: prediction of 2D monolayer structures for group VI elemental materials. These novel 2D materials are also predicted to be interesting 2D topological insulators.

•Gas Sensor: confirming with experimental collaborators that WS2 hybrid material could be a suitable gas sensor material

•Twisted bilayer systems: showing electronic properties of van der Waals materials can be tuned by twisting stackings and proposing twisted hBN could be an ideal platform to study strong correlations and Moire excitions

For exploitation and dissemination, the research results obtained in this project have been presented in several conferences and workshop. The details are listed below:
Conferences:
•2018 APS March meeting, “Square selenene and tellurene: new members of elemental 2D materials with nontrivial topological properties”
•2019 APS March Meeting, “Tuning the electronic structure and electron correlation in 2D twisted massive Dirac system: the case of twisted bilayer hBN”

Workshops:
•2018 International Workshop on synthetic elemental silicene-like materials, Marseille, “New members of elemental 2D materials: square selenene and tellurene” (Invited talk)
•2019 Max Planck Kickoff Meeting, Flatiron Institute, “Electronic properties and correlations in 2D Moire bilayers”

Especially our publication titled \"\"Large area planar stanene epitaxially grown on Ag(1 1 1)\"\" (Junji Yuhara et al 2018) received a lot of attention by the media resulting in 18 press releases in different scientific and popular websites.
The results and internal reports has also been communicated with our collaborators for further exploitations. Our collaboration with the experimental groups on the gas sensor applications with WS2 hybrid materials is a typical example of results and knowledge exploitation in this project.
The ER has also taken part in the 2018 DESY Open Day and Science Night in Hamburg and delivered scientific knowledge and introduced his research to general public and schoolchildren through informal conversations. These activities have been well received.
Research results obtained have been summarized into research papers published or to be published in scientific journals.
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Final results

The study of 2D van der waals materials will greatly advance the fields of 2D materials, condensed matter physics and electronic device applications. This project made significantly progress in understanding the electronic properties, plasmon properties and electron-electron correlations of these materials. In particular, we derived a general model to describe the plasmon dispersions and discovered localized and long lived plasmons in these systems, and showing how the plasmon properties can be tuned by different combination of heterostructures. These results expect to lay down the foundations of plasmonic applications with these amazing materials. Moreover, our study on 2D group VI elemental materials bring a new group of materials into the 2D materials family and greatly expand our knowledge on elemental 2D materials. This work is expected to further simulated theoretical and experimental efforts into the study of novel 2D materials that could be incorporated into 2D heterostructures and all 2D devices. Lastly, our work on twisted hBN predicted similar and even richer strongly physics can be studied in other twisted bilayer hBN, which open a new door for the study of highly tunable exotic strongly correlated physics in 2D van der waals materials with a twisted. Through the public engagements, such as the DESY open day, the knowledge transfer, the research and study under this Marie Curie action has considerably contributed to the better understanding of this phenomena both in the general public and the scientific community.

Website & more info

More info: https://www.mpsd.mpg.de/person/52338/166465.