Tunable Valley Splitting due to Topological Orbital Magnetic Moment in Bilayer Graphene Quantum Point Contacts
Tunable Valley Splitting due to Topological Orbital Magnetic Moment in Bilayer Graphene Quantum Point Contacts
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DOI：
10.1103/physrevlett.124.126802
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发表时间：
2020-03-24
影响因子：
8.6
通讯作者：
Rickhaus, Peter
中科院分区：
文献类型：
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作者：
Lee, Yongjin;Knothe, Angelika;Rickhaus, Peter
在多通道半导体中，谷自由度可以潜在地用于存储、操纵和读取量子信息，但其控制仍然具有挑战性。双层石墨烯中的谷可以通过由谷g因子g（v）耦合的垂直磁场来解决。然而，对gv的控制还没有得到证实。我们通过实验确定了在双层石墨烯中通过合适的栅极几何形状实现的量子点接触的能谱。使用有限偏置光谱，我们测量的能量尺度所产生的横向限制以及塞曼分裂，并找到一个自旋g因子g（s）类似于2。可以使用垂直电场将g（v）调节3倍，g（v）类似于40-120。通过考虑拓扑磁矩及其对约束和垂直位移场的依赖性的计算，定量地解释了这一结果。
In multivalley semiconductors, the valley degree of freedom can be potentially used to store, manipulate, and read quantum information, but its control remains challenging. The valleys in bilayer graphene can be addressed by a perpendicular magnetic field which couples by the valley g factor g(v). However, control over gv has not been demonstrated yet. We experimentally determine the energy spectrum of a quantum point contact realized by a suitable gate geometry in bilayer graphene. Using finite bias spectroscopy, we measure the energy scales arising from the lateral confinement as well as the Zeeman splitting and find a spin g factor g(s) similar to 2. g(v) can be tuned by a factor of 3 using vertical electric fields, g(v) similar to 40-120. The results are quantitatively explained by a calculation considering topological magnetic moment and its dependence on confinement and the vertical displacement field.