High-order fractal states in graphene superlattices

Krishna Kumar, R. and Mishchenko, A. and Chen, X. and Pezzini, S. and Auton, G.H. and Ponomarenko, L.A. and Zeitler, U. and Eaves, Laurence and Fal’ko, V.I. and Geim, A.K. (2018) High-order fractal states in graphene superlattices. Proceedings of the National Academy of Sciences, 115 (20). pp. 5135-5139. ISSN 1091-6490

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Abstract

Graphene superlattices were shown to exhibit high-temperature quantum oscillations due to periodic emergence of delocalized Bloch states in high magnetic fields such that unit fractions of the flux quantum pierce a superlattice unit cell. Under these conditions, semiclassical electron trajectories become straight again, similar to the case of zero magnetic field. Here, we report magnetotransport measurements that reveal second-, third-, and fourth-order magnetic Bloch states at high electron densities and temperatures above 100 K. The recurrence of these states creates a fractal pattern intimately related to the origin of Hofstadter butterflies. The hierarchy of the fractal states is determined by the width of magnetic minibands, in qualitative agreement with our band-structure calculations.

Item Type: Article
Keywords: Graphene; Superlattice; Hofstadter butterfly
Schools/Departments: University of Nottingham, UK > Faculty of Science > School of Physics and Astronomy
Identification Number: https://doi.org/10.1073/pnas.1804572115
Depositing User: Eprints, Support
Date Deposited: 18 May 2018 08:41
Last Modified: 02 Jul 2018 09:20
URI: http://eprints.nottingham.ac.uk/id/eprint/51866

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