Moon Pilkyung, Kim Youngwook, Koshino Mikito, Taniguchi Takashi, Watanabe Kenji, Smet Jurgen H
Arts and Sciences, NYU Shanghai, Shanghai 200124, China.
NYU-ECNU Institute of Physics at NYU Shanghai, Shanghai 200062, China.
Nano Lett. 2024 Mar 20;24(11):3339-3346. doi: 10.1021/acs.nanolett.3c04444. Epub 2024 Feb 2.
Due to Landau quantization, the conductance of two-dimensional electrons exposed to a perpendicular magnetic field exhibits oscillations that generate a fan of linear trajectories when plotted in the parameter space spanned by density and field. This fan looks identical, irrespective of the dispersion and field dependence of the Landau level energy. This is no surprise because the position of conductance minima depends solely on the level degeneracy that is linear in flux. The fractal energy spectrum that emerges within each Landau band when electrons are also exposed to a two-dimensional superlattice potential produces numerous additional oscillations, but they also create just linear fans for identical reasons. Here, we report conductance oscillations of graphene electrons exposed to a moiré potential that defy this general rule and form nonlinear trajectories in the density-field plane. We attribute this anomalous behavior to the simultaneous occupation of multiple minibands and magnetic breakdown-induced open orbits.
由于朗道量子化，暴露于垂直磁场中的二维电子的电导会出现振荡，当在由密度和磁场构成的参数空间中绘制时，这些振荡会产生一系列线性轨迹。无论朗道能级能量的色散和磁场依赖性如何，这个轨迹扇看起来都是相同的。这并不奇怪，因为电导最小值的位置仅取决于与通量呈线性关系的能级简并度。当电子还暴露于二维超晶格势时，在每个朗道带内出现的分形能谱会产生许多额外的振荡，但出于相同原因，它们也只会产生线性轨迹扇。在这里，我们报告了暴露于莫尔势的石墨烯电子的电导振荡，这种振荡违背了这一普遍规律，并在密度 - 磁场平面中形成了非线性轨迹。我们将这种异常行为归因于多个微带的同时占据以及磁击穿诱导的开放轨道。
