Hyperspectral imaging of exciton confinement within a moiré unit cell with a subnanometer electron probe

Electronic and optical excitations in two-dimensional systems are distinctly sensitive to the presence of a moiré superlattice. We used cryogenic transmission electron microscopy and spectroscopy to simultaneously image the structural reconstruction and associated localization of the lowest-energy i...

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Bibliographic Details
Published in:Science (American Association for the Advancement of Science) 2022-12, Vol.378 (6625), p.1235-1239
Main Authors: Susarla, Sandhya, Naik, Mit H, Blach, Daria D, Zipfel, Jonas, Taniguchi, Takashi, Watanabe, Kenji, Huang, Libai, Ramesh, Ramamoorthy, da Jornada, Felipe H, Louie, Steven G, Ercius, Peter, Raja, Archana
Format: Article
Language:English
Subjects:
Electron probe
Electron probes
Excitons
Heterostructures
Hyperspectral imaging
Image processing
Image reconstruction
Localization
MATERIALS SCIENCE
Optoelectronics
Spatial discrimination
Spatial resolution
Spectroscopy
Transmission electron microscopy
Transport properties
Tungsten
Tungsten disulfide
Two dimensional materials
Unit cell
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Summary:Electronic and optical excitations in two-dimensional systems are distinctly sensitive to the presence of a moiré superlattice. We used cryogenic transmission electron microscopy and spectroscopy to simultaneously image the structural reconstruction and associated localization of the lowest-energy intralayer exciton in a rotationally aligned WS -WSe moiré superlattice. In conjunction with optical spectroscopy and ab initio calculations, we determined that the exciton center-of-mass wave function is confined to a radius of approximately 2 nanometers around the highest-energy stacking site in the moiré unit cell. Our results provide direct evidence that atomic reconstructions lead to the strongly confining moiré potentials and that engineering strain at the nanoscale will enable new types of excitonic lattices.
ISSN:0036-8075
1095-9203
DOI:10.1126/science.add9294