CE09 - Nano-objets et nanomatériaux fonctionnels, interfaces

Tailoring exciton physics at the sub-nanometer scale in twist-engineered van der Waals heterostructures – TEXTURES

Submission summary

TEXTURES targets a comprehensive understanding and control of excitons (i.e., bound electron-hole pairs) in twisted van der Waals (vdW) heterostructures, i.e., stacks of 2D materials with a rotational misalignment. These systems exhibit moiré superlattices, wherein the electronic and optical properties are modulated with twist-tunable moiré wavelengths. TEXTURES is motivated by recent observations that twisted bilayers of 2D materials, in particular semiconducting transition metal dichalcogenides (TMDs), support a rich variety of moiré excitons. Engineering excitons and charge carriers in moiré superlattices holds huge promise for quantum nano-(opto)electronics; however, it comes up against major experimental difficulties. Indeed, the electronic and optical properties of vdW heterostructures are governed by intrinsic (twist angle, proximity effects) and extrinsic effects (defects, dielectric disorder, strain, atomic reconstruction), which all occur at the (sub)nanometer scale. Technological breakthroughs based on 2D materials require answers to the questions below:

How do extrinsic disorder and moiré superpotentials modify the nanoscale optical properties of 2D materials?
How do excitons localize in moiré superpotentials? What are their quantum optical properties?
How can picosecond exciton dynamics be externally controlled at the nanoscale?
Do the moiré-induced phenomena observed at low temperature still exist at room temperature?

In order to answer these questions, we will fabricate and fully characterize ultraclean vdW heterostructures with finely controlled twist angle. We will carry out optical spectroscopy measurements on these heterostructures with sub-picosecond temporal resolution and unprecedented spatial resolution down to the atomic scale, using a scanning tunneling microscope (STM) equipped with optical access. Thereby, we will address fundamental issues that are key in the development of future technologies based on moiré physics.

Project coordinator

Monsieur Stéphane Berciaud (Centre national de la recherche scientifique)

The author of this summary is the project coordinator, who is responsible for the content of this summary. The ANR declines any responsibility as for its contents.

Partner

IPCMS Centre national de la recherche scientifique
ISMO Institut des Sciences Moléculaires d'Orsay

Help of the ANR 524,971 euros
Beginning and duration of the scientific project: March 2023 - 48 Months

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