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arXiv 2006.15040cond-mat.mes-hall
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Brown-Zak费米子在石墨烯超晶格中的长程弹道输运

Long-range ballistic transport of Brown-Zak fermions in graphene superlattices

Julien Barrier, Piranavan Kumaravadivel, Roshan Krishna-Kumar, L. A. Ponomarenko, Na Xin, Matthew Holwill, Ciaran Mullan, Minsoo Kim, R. V. Gorbachev, M. D. Tho… 展开作者

Julien Barrier, Piranavan Kumaravadivel, Roshan Krishna-Kumar, L. A. Ponomarenko, Na Xin, Matthew Holwill, Ciaran Mullan, Minsoo Kim, R. V. Gorbachev, M. D. Thompson, J. R. Prance, T. Taniguchi, K. Watanabe, I. V. Grigorieva, K. S. Novoselov, A. Mishchenko, V. I. Fal'ko, A. K. Geim, A. I. Berdyugin

摘要:

在量子化磁场时,石墨烯超晶格表现出复杂的分形谱,通常被称为霍夫斯塔德蝴蝶。它可以被看作是朗道能级的集合,这些朗道能级是由布朗-扎克微带的量子化产生的,这些量子化在每个超晶格晶胞的磁通量量子的有理($p/q$)分数处重现。在这里,我们表明,在石墨烯-氮化硼超晶格,布朗-扎克费米子可以表现出超过10 $^6$ cm $^2$ V $^{-1}$ s $^{-1}$和平均自由程超过几个微米的迁移率。我们的设备的卓越品质使我们能够表明,布朗-扎克迷你带是$4q$倍简并和所有的简并(自旋,谷和迷你谷)可以解除交换相互作用低于1 K。我们还发现,在$1/q$分数的电探针放置在几微米远的弯曲阻力为负。后一个观察突出了布朗-扎克费米子是布洛赫准粒子在高场中沿着直线轨道传播的事实,就像零场中的电子一样。

英文摘要:

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.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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