(Sub)nanoscale Visualization of Reconstruction-Driven Moiré Exciton Localization and Delocalization

Abstract

Spectral fingerprints in optical absorption and emission have typically been used as a signature of exciton localization in twisted moiré bilayers. However, the mechanism by which excitons become confined to specific stacking sites and their associated optical signature is experimentally unresolved. Here, we directly visualize in real space how tuning the change in extent of structural reconstruction leads to localization and delocalization of moiré excitons in the WSe2/WS2 moiré superlattice. Using cryogenic monochromated electron energy loss spectroscopy, together with first-principles GW-Bethe Salpeter equation calculations and optical spectroscopy, we uncover the physical mechanism that drives the correlation between twist-angle-dependent structural transformations, the real-space localization of moiré excitons, and their optical signatures. Surprisingly, and in contrast to the prevailing understanding, we show that the emergence of new moiré exciton resonances in the optical spectra alone is insufficient to establish exciton localization. Instead, the extent of structural reconstruction and external strain drives exciton localization, leading to new design principles for engineering moiré excitons and strain-aware quantum optoelectronic devices.

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BibTeX RIS

BibTeX

@misc{dandu2026subnanoscale,
  title = {{(Sub)nanoscale Visualization of Reconstruction-Driven Moiré Exciton Localization and Delocalization}},
  author = {Medha Dandu and Sriram Sankar and Giovanny Espitia and Rwik Dutta and Patrick J. Hays and Daria Blach and Takashi Taniguchi and Kenji Watanabe and James R. Chelikowsky and Seth Ariel Tongay and Peter Ercius and Jordan A. Hachtel and Mit H. Naik and Archana Raja and Sandhya Susarla},
  howpublished = {arXiv},
  year = {2026},
  month = sep,
  doi = {10.48550/arxiv.2609.34104},
  eprint = {2609.34104},
  archivePrefix = {arXiv},
  url = {https://arxiv.org/abs/2609.34104},
  note = {CC BY 4.0},
}

RIS

TY  - UNPB
TI  - (Sub)nanoscale Visualization of Reconstruction-Driven Moiré Exciton Localization and Delocalization
AU  - Medha Dandu
AU  - Sriram Sankar
AU  - Giovanny Espitia
AU  - Rwik Dutta
AU  - Patrick J. Hays
AU  - Daria Blach
AU  - Takashi Taniguchi
AU  - Kenji Watanabe
AU  - James R. Chelikowsky
AU  - Seth Ariel Tongay
AU  - Peter Ercius
AU  - Jordan A. Hachtel
AU  - Mit H. Naik
AU  - Archana Raja
AU  - Sandhya Susarla
PY  - 2026
DA  - 2026/09/28
PB  - arXiv
DO  - 10.48550/arxiv.2609.34104
UR  - https://arxiv.org/abs/2609.34104
AB  - Spectral fingerprints in optical absorption and emission have typically been used as a signature of exciton localization in twisted moiré bilayers. However, the mechanism by which excitons become confined to specific stacking sites and their associated optical signature is experimentally unresolved. Here, we directly visualize in real space how tuning the change in extent of structural reconstruction leads to localization and delocalization of moiré excitons in the WSe2/WS2 moiré superlattice. Using cryogenic monochromated electron energy loss spectroscopy, together with first-principles GW-Bethe Salpeter equation calculations and optical spectroscopy, we uncover the physical mechanism that drives the correlation between twist-angle-dependent structural transformations, the real-space localization of moiré excitons, and their optical signatures. Surprisingly, and in contrast to the prevailing understanding, we show that the emergence of new moiré exciton resonances in the optical spectra alone is insufficient to establish exciton localization. Instead, the extent of structural reconstruction and external strain drives exciton localization, leading to new design principles for engineering moiré excitons and strain-aware quantum optoelectronic devices.
ER  -

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