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Research output: Contribution to Journal/Magazine › Journal article › peer-review
Research output: Contribution to Journal/Magazine › Journal article › peer-review
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TY - JOUR
T1 - Long-range ballistic transport of Brown-Zak fermions in graphene superlattices
AU - Barrier, Julien
AU - Kumaravadivel, Piranavan
AU - Kumar, Roshan Krishna
AU - Ponomarenko, Leonid
AU - Xin, Na
AU - Holwill, Matthew
AU - Mullan, Ciaran
AU - Kim, Minsoo
AU - Gorbachev, R. V.
AU - Thompson, Michael
AU - Prance, Jonathan
AU - Taniguchi, T.
AU - Watanabe, K.
AU - Grigorieva, I. V.
AU - Novoselov, K. S.
AU - Mishchenko, Artem
AU - Fal'ko, V. I.
AU - Geim, A. K.
AU - Berdyugin, A. I.
PY - 2020/11/13
Y1 - 2020/11/13
N2 - 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 106 cm2 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 1 K. 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.
AB - 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 106 cm2 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 1 K. 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.
U2 - 10.1038/s41467-020-19604-0
DO - 10.1038/s41467-020-19604-0
M3 - Journal article
VL - 11
JO - Nature Communications
JF - Nature Communications
SN - 2041-1723
M1 - 5756
ER -