Disorder-driven symmetry suppression by van der Waals planar defects in a magnetic topological insulator
Abstract
Magnetic topological insulators offer a platform to control electronic topology through magnetic order, yet reliable routes to tune their properties remain limited. Here, we show that ion irradiation allows to modify the magnetic properties and the anomalous Hall response of the van der Waals magnetic topological insulator MnBi2Te4. Using noble gas ion beams, intrinsic defects are introduced via collision cascades without chemical doping. We identify two distinct regimes. At low fluence, cation antisite disorder leads to a near-complete redistribution of Bi over cation sites while preserving long-range crystallographic order, accompanied by a transition from p-type to n-type transport. At high fluence, cation-anion intermixing drives the formation of a previously unreported layer-disordered phase characterized by a high density of van der Waals-specific planar defects, including swapped bilayers. Despite significant structural disorder, the system retains partial periodic order up to high displacement levels. Magnetometry and X-ray spectroscopy show that the Mn high-spin state and intralayer antiferromagnetic interactions likely persist, while macroscopic magnetic anisotropy is strongly reduced. At the same time, the magnitude of the anomalous Hall conductivity is reduced by an order of magnitude, far exceeding the change in magnetization, and its sign is modified. The observations are consistent with a suppression of the Berry curvature of the occupied states. These results establish ion irradiation as a means to tune anomalous Hall conductivity in topological insulators through defect engineering and reveal a disorder-driven approach to control symmetry and electronic structure in van der Waals magnetic materials.
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BibTeX
@misc{joris2026disorderdriven,
title = {{Disorder-driven symmetry suppression by van der Waals planar defects in a magnetic topological insulator}},
author = {Rikkie Joris and Heyi Xia and Ana Beatriz Pedro Fontes and Sara Bey and Seul-Ki Bac and Jiaqi Zhou and Zviadi Zarkua and Ahmed Samir Lotfy and Muhammad Saad and Philippe Ohresser and Bence G. Márkus and László Forró and Margriet van Bael and Clement Merckling and Xinyu Liu and Francisco Molina-Lopez and Jean-Christophe Charlier and Jin Won Seo and Badih A. Assaf and Lino M. C. Pereira},
howpublished = {arXiv},
year = {2026},
month = oct,
doi = {10.48550/arxiv.2605.15332},
eprint = {2605.15332},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2605.15332},
}
RIS
TY - UNPB
TI - Disorder-driven symmetry suppression by van der Waals planar defects in a magnetic topological insulator
AU - Rikkie Joris
AU - Heyi Xia
AU - Ana Beatriz Pedro Fontes
AU - Sara Bey
AU - Seul-Ki Bac
AU - Jiaqi Zhou
AU - Zviadi Zarkua
AU - Ahmed Samir Lotfy
AU - Muhammad Saad
AU - Philippe Ohresser
AU - Bence G. Márkus
AU - László Forró
AU - Margriet van Bael
AU - Clement Merckling
AU - Xinyu Liu
AU - Francisco Molina-Lopez
AU - Jean-Christophe Charlier
AU - Jin Won Seo
AU - Badih A. Assaf
AU - Lino M. C. Pereira
PY - 2026
DA - 2026/10/09
PB - arXiv
DO - 10.48550/arxiv.2605.15332
UR - https://arxiv.org/abs/2605.15332
AB - Magnetic topological insulators offer a platform to control electronic topology through magnetic order, yet reliable routes to tune their properties remain limited. Here, we show that ion irradiation allows to modify the magnetic properties and the anomalous Hall response of the van der Waals magnetic topological insulator MnBi_2Te_4. Using noble gas ion beams, intrinsic defects are introduced via collision cascades without chemical doping. We identify two distinct regimes. At low fluence, cation antisite disorder leads to a near-complete redistribution of Bi over cation sites while preserving long-range crystallographic order, accompanied by a transition from p-type to n-type transport. At high fluence, cation-anion intermixing drives the formation of a previously unreported layer-disordered phase characterized by a high density of van der Waals-specific planar defects, including swapped bilayers. Despite significant structural disorder, the system retains partial periodic order up to high displacement levels. Magnetometry and X-ray spectroscopy show that the Mn high-spin state and intralayer antiferromagnetic interactions likely persist, while macroscopic magnetic anisotropy is strongly reduced. At the same time, the magnitude of the anomalous Hall conductivity is reduced by an order of magnitude, far exceeding the change in magnetization, and its sign is modified. The observations are consistent with a suppression of the Berry curvature of the occupied states. These results establish ion irradiation as a means to tune anomalous Hall conductivity in topological insulators through defect engineering and reveal a disorder-driven approach to control symmetry and electronic structure in van der Waals magnetic materials.
ER -