Varlet Anastasia, Liu Ming-Hao, Krueckl Viktor, Bischoff Dominik, Simonet Pauline, Watanabe Kenji, Taniguchi Takashi, Richter Klaus, Ensslin Klaus, Ihn Thomas
Solid State Physics Laboratory, ETH Zürich, 8093 Zürich, Switzerland.
Institut für Theoretische Physik, Universität Regensburg, D-93040 Regensburg, Germany.
Phys Rev Lett. 2014 Sep 12;113(11):116601. doi: 10.1103/PhysRevLett.113.116601. Epub 2014 Sep 8.
We report the experimental observation of Fabry-Pérot interference in the conductance of a gate-defined cavity in a dual-gated bilayer graphene device. The high quality of the bilayer graphene flake, combined with the device's electrical robustness provided by the encapsulation between two hexagonal boron nitride layers, allows us to observe ballistic phase-coherent transport through a 1-μm-long cavity. We confirm the origin of the observed interference pattern by comparing to tight-binding calculations accounting for the gate-tunable band gap. The good agreement between experiment and theory, free of tuning parameters, further verifies that a gap opens in our device. The gap is shown to destroy the perfect reflection for electrons traversing the barrier with normal incidence (anti-Klein tunneling). The broken anti-Klein tunneling implies that the Berry phase, which is found to vary with the gate voltages, is always involved in the Fabry-Pérot oscillations regardless of the magnetic field, in sharp contrast with single-layer graphene.
我们报告了在双栅极双层石墨烯器件中，对栅极定义腔的电导进行法布里-珀罗干涉的实验观察结果。高质量的双层石墨烯薄片，与由两个六方氮化硼层之间的封装所提供的器件电稳定性相结合，使我们能够观察到通过一个1微米长的腔的弹道相相干输运。通过与考虑栅极可调带隙的紧束缚计算结果进行比较，我们证实了所观察到的干涉图案的来源。实验与理论之间的良好一致性，且无需调整参数，进一步验证了我们的器件中出现了带隙。该带隙被证明会破坏电子垂直入射穿过势垒时的完美反射（反克莱因隧穿）。与单层石墨烯形成鲜明对比的是，反克莱因隧穿的破坏意味着，尽管存在磁场，但发现随栅极电压变化的贝里相位始终参与法布里-珀罗振荡。
