期刊
NATURE COMMUNICATIONS
卷 11, 期 1, 页码 -出版社
NATURE RESEARCH
DOI: 10.1038/s41467-020-19604-0
关键词
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资金
- Engineering and Physical Sciences Research Council (EPSRC) [EP/N010345]
- Lloyd's Register Foundation
- Royal Society
- European Research Council
- Graphene NOWNANO Doctoral Training Centre
- Graphene Flagship
- EPSRC [EP/K005014/1, 2109254] Funding Source: UKRI
In quantizing magnetic fields, graphene superlattices exhibit a complex fractal spectrum often referred to as the Hofstadter butterfly. It can be viewed as a collection of Landau levels that arise from quantization of Brown-Zak minibands recurring at rational (p/q) fractions of the magnetic flux quantum per superlattice unit cell. Here we show that, in graphene-on-boron-nitride superlattices, Brown-Zak fermions can exhibit mobilities above 10(6)cm(2)V(-1)s(-1) and the mean free path exceeding several micrometers. The exceptional quality of our devices allows us to show that Brown-Zak minibands are 4q times degenerate and all the degeneracies (spin, valley and mini-valley) can be lifted by exchange interactions below 1K. We also found negative bend resistance at 1/q fractions for electrical probes placed as far as several micrometers apart. The latter observation highlights the fact that Brown-Zak fermions are Bloch quasiparticles propagating in high fields along straight trajectories, just like electrons in zero field. Here, the authors show that Brown-Zak fermions in graphene-on-boron-nitride superlattices exhibit mobilities above 10(6)cm(2)/V s and micrometer scale ballistic transport.
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