Liu Yi-Wen, Su Ying, Zhou Xiao-Feng, Yin Long-Jing, Yan Chao, Li Si-Yu, Yan Wei, Han Sheng, Fu Zhong-Qiu, Zhang Yu, Yang Qian, Ren Ya-Ning, He Lin
Center for Advanced Quantum Studies, Department of Physics, Beijing Normal University, Beijing 100875, People's Republic of China.
Theoretical Division, T-4 and CNLS, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA.
Phys Rev Lett. 2020 Dec 4;125(23):236102. doi: 10.1103/PhysRevLett.125.236102.
The interplay between interlayer van der Waals interaction and intralayer lattice distortion can lead to structural reconstruction in slightly twisted bilayer graphene (TBG) with the twist angle being smaller than a characteristic angle θ_{c}. Experimentally, the θ_{c} is demonstrated to be very close to the magic angle (θ≈1.08°). Here we address the transition between reconstructed and unreconstructed structures of the TBG across the magic angle by using scanning tunneling microscopy (STM). Our experiment demonstrates that both structures are stable in the TBG around the magic angle. By using a STM tip, we show that the two structures can be changed to each other and a triangular network of chiral one-dimensional states hosted by domain boundaries can be switched on and off. Consequently, the bandwidth of the flat band, which plays a vital role in the emergent strongly correlated states in the magic angle TBG, is tuned. This provides an extra control knob to manipulate the exotic electronic states of the TBG near the magic angle.
层间范德华相互作用与层内晶格畸变之间的相互作用，会导致扭曲角小于特征角θc的轻微扭曲双层石墨烯（TBG）发生结构重构。实验表明，θc非常接近魔角（θ≈1.08°）。在此，我们利用扫描隧道显微镜（STM）研究了TBG在魔角附近重构结构与未重构结构之间的转变。我们的实验表明，这两种结构在魔角附近的TBG中都是稳定的。通过使用STM针尖，我们发现这两种结构可以相互转变，并且由畴界承载的手性一维态的三角形网络可以打开和关闭。因此，在魔角TBG中出现的强关联态中起关键作用的平带带宽得到了调控。这为操纵魔角附近TBG的奇异电子态提供了一个额外的控制旋钮。
