PerspectiveTwisted Graphene

Ferromagnetism in magic-angle graphene

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Science  09 Aug 2019:
Vol. 365, Issue 6453, pp. 543
DOI: 10.1126/science.aay3409

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Summary

The mechanical exfoliation of graphite to form graphene (1) opened the door for isolating and stacking other two-dimensional (2D) materials to build devices with specific functionality. In 2010, it was discovered that introducing a twist between the crystal orientations of two stacked graphene layers can drastically change the electronic properties of the material (2), and ultimately, precise control of the twist angle θ was realized (3). These materials have many emergent electronic properties. For instance, at a specific “magic” twist angle, correlated insulated phases (4) and superconductivity (5) were found and replicated (6, 7). On page 605 of this issue, Sharpe et al. (8) demonstrate that the correlated insulator phase at three-quarters filling of a unit cell in magic-angle graphene is a ferromagnetic insulator that hosts conducting states on its boundary, suggesting an emergent topology.

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