Institute of Nanotechnology, Karlsruhe Institute of Technology (KIT), D-76021 Karlsruhe, Germany.
Department of Physics, National Cheng Kung University, Tainan 70101, Taiwan.
Phys Rev Lett. 2018 Sep 21;121(12):127706. doi: 10.1103/PhysRevLett.121.127706.
We show that in gapped bilayer graphene, quasiparticle tunneling and the corresponding Berry phase can be controlled such that they exhibit features of single-layer graphene such as Klein tunneling. The Berry phase is detected by a high-quality Fabry-Pérot interferometer based on bilayer graphene. By raising the Fermi energy of the charge carriers, we find that the Berry phase can be continuously tuned from 2π down to 0.68π in gapped bilayer graphene, in contrast to the constant Berry phase of 2π in pristine bilayer graphene. Particularly, we observe a Berry phase of π, the standard value for single-layer graphene. As the Berry phase decreases, the corresponding transmission probability of charge carriers at normal incidence clearly demonstrates a transition from anti-Klein tunneling to nearly perfect Klein tunneling.
我们表明，在带隙双层石墨烯中，准粒子隧道和相应的 Berry 相位可以得到控制，从而表现出单层石墨烯的特征，如 Klein 隧道。Berry 相位通过基于双层石墨烯的高质量法布里-珀罗干涉仪来检测。通过提高载流子的费米能，我们发现 Berry 相位可以从带隙双层石墨烯中的 2π连续调谐到 0.68π，而原始双层石墨烯中的 Berry 相位是常数 2π。特别地，我们观察到 Berry 相位为 π，这是单层石墨烯的标准值。随着 Berry 相位的减小，在正常入射时载流子的相应透射率明显表现出从反 Klein 隧道到近乎完美 Klein 隧道的转变。
