Department of Physics, Massachusetts Institute of Technology, 77 Massachusetts Ave, Cambridge, Massachusetts 02139, USA.
Phys Rev Lett. 2011 Feb 11;106(6):066601. doi: 10.1103/PhysRevLett.106.066601. Epub 2011 Feb 9.
We describe a new regime of magnetotransport in two-dimensional electron systems in the presence of a narrow potential barrier. In such systems, the Landau level states, which are confined to the barrier region in strong magnetic fields, undergo a deconfinement transition as the field is lowered. Transport measurements on a top-gated graphene device are presented. Shubnikov-de Haas (SdH) oscillations, observed in the unipolar regime, are found to abruptly disappear when the strength of the magnetic field is reduced below a certain critical value. This behavior is explained by a semiclassical analysis of the transformation of closed cyclotron orbits into open, deconfined trajectories.
我们描述了二维电子系统中存在窄势垒时的一种新的磁输运机制。在这种系统中，随着磁场的降低，被限制在势垒区域内的朗道能级状态会经历去禁闭相变。我们提出了一种基于顶部栅控石墨烯器件的输运测量方法。在单极性区域观察到的舒布尼科夫-德哈斯（Shubnikov-de Haas，SdH）振荡，当磁场强度降低到一定临界值以下时，会突然消失。这种行为可以通过对封闭的回旋轨道转化为开放的、去禁闭的轨迹的半经典分析来解释。
