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PreprintCC BY 4.0arXiv

Restoring the Surface Magnetic Gap in MnBi2Te4

  • Ce Bian
  • Hengxin Tan
  • Wenhui Duan
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Abstract

A widespread experimental realization of quantized anomalous transport in the intrinsic magnetic topological insulator MnBi2Te4 is hindered by its elusive surface magnetic gap. Uncovering the origin of the gapless states is essential for accessing its topological properties. Here we show that surface defects lower the electrostatic potential, drive topological surface states into subsurface layers, suppress exchange interactions, thereby closing the gap. Tuning the surface electrostatic potential via external electric fields or interfacial fields in van der Waals heterostructures restores the expected gap and enables control of its topology. This is confirmed by model calculations and validated in defective MnBi2Te4 films interfaced with polar insulators, explaining the enhanced quantum anomalous Hall effect under AlOx capping observed in recent experiments. Our theory identifies electrostatically driven surface-state delocalization as a competitive origin of gap suppression and proposes displacement-field engineering for robust quantized transport.

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Cite

BibTeXRIS
BibTeX
@misc{bian2026restoring,
  title = {{Restoring the Surface Magnetic Gap in MnBi$_2$Te$_4$}},
  author = {Ce Bian and Hengxin Tan and Wenhui Duan},
  howpublished = {arXiv},
  year = {2026},
  month = sep,
  doi = {10.48550/arxiv.2609.06915},
  eprint = {2609.06915},
  archivePrefix = {arXiv},
  url = {https://arxiv.org/abs/2609.06915},
  note = {CC BY 4.0},
}
RIS
TY  - UNPB
TI  - Restoring the Surface Magnetic Gap in MnBi_2Te_4
AU  - Ce Bian
AU  - Hengxin Tan
AU  - Wenhui Duan
PY  - 2026
DA  - 2026/09/07
PB  - arXiv
DO  - 10.48550/arxiv.2609.06915
UR  - https://arxiv.org/abs/2609.06915
AB  - A widespread experimental realization of quantized anomalous transport in the intrinsic magnetic topological insulator MnBi_2Te_4 is hindered by its elusive surface magnetic gap. Uncovering the origin of the gapless states is essential for accessing its topological properties. Here we show that surface defects lower the electrostatic potential, drive topological surface states into subsurface layers, suppress exchange interactions, thereby closing the gap. Tuning the surface electrostatic potential via external electric fields or interfacial fields in van der Waals heterostructures restores the expected gap and enables control of its topology. This is confirmed by model calculations and validated in defective MnBi_2Te_4 films interfaced with polar insulators, explaining the enhanced quantum anomalous Hall effect under AlO_x capping observed in recent experiments. Our theory identifies electrostatically driven surface-state delocalization as a competitive origin of gap suppression and proposes displacement-field engineering for robust quantized transport.
ER  -