Valley splitter and transverse valley focusing in twisted bilayer graphene
Valley splitter and transverse valley focusing in twisted bilayer graphene
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DOI：
10.1103/physrevresearch.2.043151
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发表时间：
2019-12
期刊：
影响因子：
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通讯作者：
C. De Beule;P. Silvestrov;Ming-Hao Liu;P. Recher
中科院分区：
文献类型：
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作者：
C. De Beule;P. Silvestrov;Ming-Hao Liu;P. Recher
我们研究了扭曲双层石墨烯中的输运，并表明静电屏障可以作为谷分离器，其中来自K谷的电子仅传输到例如顶层（底层），从而导致谷层锁定电流。我们表明，当势垒在云纹尺度上缓慢变化并引起跨结的Lifshitz跃迁（即费米表面拓扑的变化）时，可以获得这样的谷分裂。此外，我们表明，对于给定的山谷，反射和透射电流横向偏转，因为时间反转对称性在每个山谷中分别被有效地打破，导致在零磁场下山谷选择横向聚焦。
We study transport in twisted bilayer graphene and show that electrostatic barriers can act as valley splitters, where electrons from the $K$ ($K'$) valley are transmitted only to e.g.\ the top (bottom) layer, leading to valley-layer locked currents. We show that such a valley splitter is obtained when the barrier varies slowly on the moire scale and induces a Lifshitz transition across the junction, i.e.\ a change in the Fermi surface topology. Furthermore, we show that for a given valley the reflected and transmitted current are transversely deflected, as time-reversal symmetry is effectively broken in each valley separately, resulting in valley-selective transverse focusing at zero magnetic field.