Conti Sara, Chaves Andrey, Pandey Tribhuwan, Covaci Lucian, Peeters François M, Neilson David, Milošević Milorad V
Department of Physics, University of Antwerp, Groenenborgerlaan 171, Antwerp 2020, Belgium.
Departamento de Física, Universidade Federal do Ceará, Caixa Postal 6030, Fortaleza 60455-760, Brazil.
Nanoscale. 2023 Sep 1;15(34):14032-14042. doi: 10.1039/d3nr01183f.
We explore the flatness of conduction and valence bands of interlayer excitons in MoS/WSe van der Waals heterobilayers, tuned by interlayer twist angle, pressure, and external electric field. We employ an efficient continuum model where the moiré pattern from lattice mismatch and/or twisting is represented by an equivalent mesoscopic periodic potential. We demonstrate that the mismatch moiré potential is too weak to produce significant flattening. Moreover, we draw attention to the fact that the quasi-particle effective masses around the Γ-point and the band flattening are with twisting. As an alternative approach, we show (i) that reducing the interlayer distance by uniform vertical pressure can significantly increase the effective mass of the moiré hole, and (ii) that the moiré depth and its band flattening effects are strongly enhanced by accessible electric gating fields perpendicular to the heterobilayer, with resulting electron and hole effective masses increased by more than an order of magnitude - leading to record-flat bands. These findings impose boundaries on the commonly generalized benefits of moiré twistronics, while also revealing alternative feasible routes to achieve truly flat electron and hole bands to carry us to strongly correlated excitonic phenomena on demand.
我们研究了通过层间扭转角、压力和外部电场调节的MoS/WSe范德华异质双层中层间激子的导带和价带的平坦度。我们采用了一种有效的连续介质模型，其中晶格失配和/或扭转产生的莫尔条纹由等效的介观周期势表示。我们证明失配莫尔势太弱，无法产生显著的平坦化。此外，我们提请注意这样一个事实，即Γ点附近的准粒子有效质量和能带平坦度与扭转有关。作为一种替代方法，我们表明：（i）通过均匀垂直压力减小层间距离可以显著增加莫尔空穴的有效质量；（ii）垂直于异质双层的可及电场能强烈增强莫尔深度及其能带平坦化效应，使电子和空穴有效质量增加超过一个数量级——从而产生创纪录的平坦能带。这些发现为莫尔自旋电子学普遍推广的益处设定了界限，同时也揭示了实现真正平坦的电子和空穴能带的其他可行途径，以按需引领我们进入强关联激子现象。
