Physics Department, University of Arizona, Tucson, AZ, 85721, USA.
College of Optical Sciences, University of Arizona, Tucson, AZ, 85721, USA.
Sci Rep. 2017 Aug 8;7(1):7611. doi: 10.1038/s41598-017-07580-3.
The electronic band structure of twisted bilayer graphene develops van Hove singularities whose energy depends on the twist angle between the two layers. Using Raman spectroscopy, we monitor the evolution of the electronic band structure upon doping using the G peak area which is enhanced when the laser photon energy is resonant with the energy separation of the van Hove singularities. Upon charge doping, the Raman G peak area initially increases for twist angles larger than a critical angle and decreases for smaller angles. To explain this behavior with twist angle, the energy separation of the van Hove singularities must decrease with increasing charge density demonstrating the ability to modify the electronic and optical properties of twisted bilayer graphene with doping.
扭曲双层石墨烯的电子能带结构会出现范霍夫奇点，其能量取决于两层之间的扭转角度。我们使用拉曼光谱法，通过监测激光光子能量与范霍夫奇点能量差共振时 G 峰面积的变化来研究掺杂时电子能带结构的演化。在电荷掺杂下，当扭转角大于临界角时，拉曼 G 峰面积最初增加，而当扭转角较小时，其面积会减小。为了解释这种随扭转角变化的行为，范霍夫奇点的能量差必须随电荷密度的增加而减小，这表明可以通过掺杂来改变扭曲双层石墨烯的电子和光学性质。
