论文标题
Moiré激子在Van der Waals异质结构中的可调阶段
Tunable Phases of Moiré Excitons in van der Waals Heterostructures
论文作者
论文摘要
将过渡金属二分法的单层堆叠到具有有限扭曲角的异质结构中，会产生具有可调周期性的人造Moiré超晶格。因此，激子具有周期性的潜力，可以利用这些潜力来量身定制这些材料的光电特性。虽然最近的实验研究证实了扭曲依赖性光谱，但尚未完全阐明Moiré激子共振的微观起源。在这里，我们将第一个原理计算与激子密度矩阵形式主义相结合，以研究不同的Moiré激子阶段之间的过渡及其对扭曲的摩西$ _2 $/WSE $ _2 $ _2 $ HETEROSTRUCTURE的光学性质的影响。在小于2 $^{\ circ} $的角度，我们找到了平坦的莫伊尔（Moiré），以捕获层间和内部的激子。这个Moiré激子阶段大幅度地变成了已经以3 $^{\ CRICC} $的完全离域状态变化。我们分别预测了莫伊尔捕获和离域的激子阶段的激子共振的线性和二次扭转依赖性。我们的工作提供了微观见解，可以在Van der Waals超级晶格中量身定制Moiré激子阶段。
Stacking monolayers of transition metal dichalcogenides into a heterostructure with a finite twist-angle gives rise to artificial moiré superlattices with a tunable periodicity. As a consequence, excitons experience a periodic potential, which can be exploited to tailor optoelectronic properties of these materials. While recent experimental studies have confirmed twist-angle dependent optical spectra, the microscopic origin of moiré exciton resonances has not been fully clarified yet. Here, we combine first principle calculations with the excitonic density matrix formalism to study transitions between different moiré exciton phases and their impact on optical properties of the twisted MoSe$_2$/WSe$_2$ heterostructure. At angles smaller than 2$^{\circ}$ we find flat, moiré trapped states for inter- and intralayer excitons. This moiré exciton phase drastically changes into completely delocalized states already at 3$^{\circ}$. We predict a linear and quadratic twist-angle dependence of excitonic resonances for the moiré-trapped and delocalized exciton phase, respectively. Our work provides microscopic insights opening the possibility to tailor moiré exciton phases in van der Waals superlattices.
