Physics Research Seminar

Tobias Wolf (ETH Zürich, Switzerland) will give the seminar "Metamaterials from Twisted Honeycomb Lattices" about his research.
Hosted by Prof. Jose Lado (Department of Applied Physics).

Everyone interested welcome!
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Twisted honeycomb lattices provide a versatile platform to engineer metamaterials with novel emergent properties. In these structures, the resulting geometric moire superlattice induces long-wavelength modulations that rearrange the electronic spectrum into minibands. Paradigmatic realizations are graphene on hexa-boron nitride (G/hBN) and twisted bilayer graphene (TBG). Firstly, for G/hBN-like systems [1], we will analyze all symmetry-allowed modulations and systematically classify the parameter space via gap-closing transitions in the low-energy spectrum. We will find criteria for protected degeneracies and for (valley) topological band gaps. Secondly, for TBG [2], we will see that tuning the twist angle to 𝛼∗ ≈ 0.8◦ generates flat bands away from charge neutrality that have a magnetic instability at half-filling. We will find that the magnetic correlations can be tuned electrically by applying an interlayer bias. Our results exemplify a powerful playground to control the topological and magnetic properties of graphene by means of moire engineering.

[1] T. M. R. Wolf, O. Zilberberg, I. Levkivskyi, and G. Blatter, Physical Review B 98, 125408 (2018)
[2] T. M. R. Wolf, J. L. Lado, G. Blatter, and O. Zilberberg, Physical Review Letters 123, 096802 (2019)

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