Imaging topological polar structures in marginally twisted 2D semiconductors
Moiré superlattices formed in van der Waals heterostructures by twisting, lattice mismatch and strain present an opportunity for creating metamaterials with unique properties absent in the individual layers. Ferroelectricity for example, arises from broken inversion symmetry in twisted and strained bilayers of 2D semiconductors with stacking domains of alternating out-of-plane polarization. However, the individual contributions of twist and strain to the formation of topological polar nanostructures remain unclear and experimentally challenging to resolve. Inversion symmetry breaking is predicted to generate in-plane polarization along the domain walls, forming topologically non-trivial Bloch-type merons (half-skyrmions) in twisted systems and Néel-type merons in strained systems. Here we utilize angle-resolved vector piezoresponse force microscopy to spatially resolve polarization components and topological polar nanostructures in marginally twisted bilayer WSe 2 , providing experimental evidence of topologically non-trivial meron/antimeron structures. This approach can be used to distinguish Bloch-type, Néel-type and hybrid structures, allowing us to quantify the separate contributions of strain and twist in a moiré superlattice, opening pathways for exploring twist-induced topology in engineered nano-devices.
Authors
- Md Hemayet Uddin (ORCID: https://orcid.org/0000-0003-3618-9653)
- Kaijian Xing (ORCID: https://orcid.org/0000-0001-5254-4710)
- Jack B. Muir (ORCID: https://orcid.org/0000-0003-2617-3420)
- Takashi Taniguchi (ORCID: https://orcid.org/0000-0003-0017-7669)
- Seng Huat Lee (ORCID: https://orcid.org/0000-0003-4254-3460)
- Pankaj Sharma (ORCID: https://orcid.org/0000-0002-9130-9235)
- Thi‐Hai‐Yen Vu (ORCID: https://orcid.org/0000-0002-8453-3271)
- Jeffrey A. Davis (ORCID: https://orcid.org/0000-0003-4537-4084)
- Kenji Watanabe (ORCID: https://orcid.org/0000-0003-3701-8119)
- Mark T. Edmonds (ORCID: https://orcid.org/0000-0001-8054-5470)
- Zhiqiang Mao (ORCID: https://orcid.org/0000-0002-4920-3293)
- Michael S. Fuhrer (ORCID: https://orcid.org/0000-0001-6183-2773)
- Shaffique Adam (ORCID: https://orcid.org/0000-0002-3095-9920)
- Daniel Bennett
- Gayani Nadeera Pallewella
- Linnan Jia
Institutions
- Pennsylvania State University (US)
- Harvard University (US)
- National University of Singapore (SG)
- Flinders University (AU)
- Nanyang Technological University (SG)
- Washington University in St. Louis (US)
- National Institute for Materials Science (JP)
- Melbourne Centre for Nanofabrication (AU)
- Australian National Fabrication Facility (AU)
- ARC Centre of Excellence in Future Low-Energy Electronics Technologies (AU)
- Monash University (AU)
- Swinburne University of Technology (AU)
Publication Details
- Journal
- Science Advances
- Published
- 2026-09-11
- DOI
- https://doi.org/10.1126/sciadv.aed8555
- Citations
- 3
- Primary Topic
- Quantum and electron transport phenomena
- Type
- article
- Field-Weighted Citation Impact
- 0.00
Funders
- National Science Foundation
- Simons Foundation
- University of Pennsylvania
- Australian National Fabrication Facility
- Pennsylvania State University
- National Research Foundation
- National Research Foundation Singapore
- Nanyang Technological University
- Ministry of Education, Culture, Sports, Science and Technology
- Multidisciplinary University Research Initiative
- Australian Research Council
- Japan Society for the Promotion of Science
- Division of Materials Research
- Army Research Office