论文标题
旋转单层双层石墨烯中的栅极可调拓扑平坦带
Gate tunable topological flat bands in twisted monolayer-bilayer graphene
论文作者
论文摘要
我们研究了双层石墨烯（TGBG）上扭曲的单层双层石墨烯（TMBG）或扭曲石墨烯的带状结构，这是扭曲角度和垂直电场的函数，以搜索实现孤立的几乎平坦带的最佳条件。狭窄的带宽比有效的库仑能量可比性或小，可满足$ u _ {\ textrm {fextrm {eff}} /w \ gtrsim 1 $ 1 $，在$ 0.3^{\ circ} \ sim 1.5^{\ sim Circ} $中，在$ 0.3^{\ circ} $ 0.5} $ 0.5^} \ sim crock twist范围内，\ sim 1.5^{\ sim cimp crock。 0.85^{\ circ}，\，1.3^{\ circ} $用于适当的垂直电场磁场和方向。电子孔不对称带的谷地数本质上取决于双层石墨烯中跳术语的细节，并外部取决于电场或与接触六边形的硝基氮化物氮化物底物等对齐的石墨烯层中电场或平均交错电位的因素。带隔离，带宽和山谷Chern号的这种可调节性使TMBG具有比扭曲的双层石墨烯更通用的系统，用于寻找容易与强相关性的近乎平坦的频带。
We investigate the band structure of twisted monolayer-bilayer graphene (tMBG), or twisted graphene on bilayer graphene (tGBG), as a function of twist angles and perpendicular electric fields in search of optimum conditions for achieving isolated nearly flat bands. Narrow bandwidths comparable or smaller than the effective Coulomb energies satisfying $U_{\textrm{eff}} /W \gtrsim 1$ are expected for twist angles in the range of $0.3^{\circ} \sim 1.5^{\circ}$, more specifically in islands around $θ\sim 0.5^{\circ}, \, 0.85^{\circ}, \,1.3^{\circ}$ for appropriate perpendicular electric field magnitudes and directions. The valley Chern numbers of the electron-hole asymmetric bands depend intrinsically on the details of the hopping terms in the bilayer graphene, and extrinsically on factors like electric fields or average staggered potentials in the graphene layer aligned with the contacting hexagonal boron nitride substrate. This tunability of the band isolation, bandwidth, and valley Chern numbers makes of tMBG a more versatile system than twisted bilayer graphene for finding nearly flat bands prone to strong correlations.
