1] Department of Physics, University of Basel, Klingelbergstrasse 82, CH-4056 Basel, Switzerland [2].
Nat Commun. 2013;4:2342. doi: 10.1038/ncomms3342.
The low-energy electronic excitations in graphene are described by massless Dirac fermions that have a linear dispersion relation. Taking advantage of this 'optics-like' electron dynamics, generic optical elements like lenses and wave guides have been proposed for electrons in graphene. Tuning of these elements relies on the ability to adjust the carrier concentration in defined areas. However, the combination of ballistic transport and complex gating remains challenging. Here we report on the fabrication and characterization of suspended graphene p-n junctions. By local gating, resonant cavities can be defined, leading to complex Fabry-Pérot interferences. The observed conductance oscillations account for quantum interference of electrons propagating ballistically over distances exceeding 1 μm. Visibility of the interferences is demonstrated to be enhanced by Klein collimation at the p-n interface. This finding paves the way to more complex gate-controlled ballistic graphene devices and brings electron optics in graphene closer to reality.
石墨烯中的低能电子激发由无质量狄拉克费米子描述，它们具有线性色散关系。利用这种“类光学”电子动力学，已经为石墨烯中的电子提出了通用的光学元件，如透镜和波导。这些元件的调谐依赖于在定义的区域内调节载流子浓度的能力。然而，弹道传输和复杂的门控的结合仍然具有挑战性。在这里，我们报告了悬浮石墨烯 p-n 结的制造和特性。通过局部门控，可以定义共振腔，导致复杂的法布里-珀罗干涉。观察到的电导振荡表明，电子在超过 1μm 的距离上弹道传播的量子干涉。证明了 p-n 界面处的克莱因准直增强了干涉的可见度。这一发现为更复杂的栅控弹道石墨烯器件铺平了道路，并使石墨烯中的电子光学更接近现实。
