Lee Yongjin, Knothe Angelika, Overweg Hiske, Eich Marius, Gold Carolin, Kurzmann Annika, Klasovika Veronika, Taniguchi Takashi, Wantanabe Kenji, Fal'ko Vladimir, Ihn Thomas, Ensslin Klaus, Rickhaus Peter
Department of Physics, ETH Zurich, Otto-Stern-Weg 1, 8093 Zurich, Switzerland.
National Graphene Institute, University of Manchester, Manchester M13 9PL, United Kingdom.
Phys Rev Lett. 2020 Mar 27;124(12):126802. doi: 10.1103/PhysRevLett.124.126802.
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 g_{v} 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}∼2. g_{v} can be tuned by a factor of 3 using vertical electric fields, g_{v}∼40-120. The results are quantitatively explained by a calculation considering topological magnetic moment and its dependence on confinement and the vertical displacement field.
在多能谷半导体中，谷自由度有潜力用于存储、操控和读取量子信息，但其控制仍具有挑战性。双层石墨烯中的谷可通过与谷g因子gv耦合的垂直磁场来调控。然而，尚未证明对gv的控制。我们通过实验确定了双层石墨烯中由合适的栅极几何结构实现的量子点接触的能谱。利用有限偏置光谱，我们测量了横向限制以及塞曼分裂产生的能量尺度，并发现自旋g因子gs约为2。使用垂直电场可将gv调节3倍，gv约为40 - 120。通过考虑拓扑磁矩及其对限制和垂直位移场的依赖性的计算，对结果进行了定量解释。
