Tunable two-dimensional superlattices in graphene

Robin Huber, Ming-Hao Liu, Szu-Chao Chen, Martin Drienovsky, Andreas Sandner, Kenji Watanabe, Takashi Taniguchi, Klaus Richter, Dieter Weiss, Jonathan Eroms

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Mar 18, 2020
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Received Date: 2nd March 20

Electrons in an artificially created periodic potential - a superlattice - follow Bloch’s theorem, and they reside in minibands. This approach is particularly suitable to study effects inaccessible in natural crystals, such as Hofstadter’s butterfly. After pioneering experiments using high-mobility GaAs based superlattices, additional proof came with graphene-hexagonal boron nitride (hBN) heterostructures forming moiré superlattices. However, both lattice symmetry and period are constrained by the crystal lattices of graphene and hBN, and the exact potential is governed by, e.g., strain or local band-gaps, which are virtually impossible to be controlled experimentally. A first approach to circumvent this was recently presented by Forsythe et al., who employed a patterned dielectric, and demonstrated gate-tunable superlattice effects. In this work, combining patterned and uniform gates, we demonstrate satellite resistance peaks corresponding to Dirac cones to fourth order, and the Hofstadter butterfly, including the non-monotonic quantum Hall response predicted by Thouless et al. The exact potential shape can be determined from elementary electrostatics, allowing for a detailed comparison between miniband structureand calculated transport characteristics. We thus present a comprehensive picture of graphene-based superlattices, featuring a broad range of miniband effects, both inexperiment and in our theoretical modeling

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This is an abstract of a preprint hosted on an independent third party site. It has not been peer reviewed but is currently under consideration at Nature Communications.

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