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In twisted graphene, some electrons are heavier than others

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Why This Matters

Recent research on twisted bilayer graphene reveals that electrons in this material can exhibit varying effective masses depending on their momentum, challenging previous assumptions of uniform 'heavy' electrons. This discovery enhances our understanding of the complex electronic behaviors in 2D materials, potentially paving the way for advanced quantum technologies and novel electronic devices.

Key Takeaways

Introducing a small twist angle between two graphene layers (2D sheets of carbon atoms) that are stacked on top of each other can drastically change the material’s properties. A striking example of this occurs when a twist angle of about 1.1 degrees is used, producing a material known as magic-angle twisted bilayer graphene (MATBG). MATBG exhibits unusual properties, including unconventional superconductivity1, originating from the formation of ‘flat bands’, in which the electron’s energy is almost independent of its momentum. As a result, the electrons move slowly, interact strongly with each other and behave as if they have a large mass. In a paper in Nature, Xiao et al.2 show that this picture is incomplete: for some momenta, electrons in MATBG are heavy and interact strongly, but for others they are light and mobile.

Nature 653, 31-32 (2026)

doi: https://doi.org/10.1038/d41586-026-01154-y

References Cao, Y. et al. Nature 556, 43–50 (2018). Xiao, J. et al. Nature 653, 68–75 (2026). Rozen, A. et al. Nature 592, 214–219 (2021). Saito, Y. et al. Nature 592, 220–224 (2021). Wong, D. et al. Nature 582, 198–202 (2020). Zondiner, U. et al. Nature 582, 203–208 (2020). Song, Z.-D. & Bernevig, B. A. Phys. Rev. Lett. 129, 047601 (2022). Inbar, A. et al. Nature 614, 682–687 (2023). Bistritzer, R. & MacDonald, A. H. Proc. Natl Acad. Sci. USA 108, 12233–12237 (2011). Li, Q. et al. Nature Mater. 23, 1070–1076 (2024). Download references

Competing Interests The authors declare no competing interests.

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