菱面石墨烯超晶格中的“莫尔电容效应”与分形陈绝缘体的稳定化
The "Moiré Capacitor Effect" and Stabilization of Fractional Chern Insulators in Rhombohedral Graphene Superlattices
AI总结：
本研究提出莫尔电容效应机制，推导其解析形式并结合多带精确对角化计算，解释菱面石墨烯超晶格中FCIs在对准样品的稳定机制及未对准样品中缺失的原因。
AI中文摘要：
尽管菱面石墨烯-hBN超晶格中分形陈绝缘体（FCIs）对莫尔势的必要性已被实验证实（最初由文献1预测），但其起源与重要性的理论仍未明确。我们提出一种机制——莫尔电容效应，该效应通过将价电荷密度静电印记到导带上来增强莫尔势。我们推导了该项的解析形式，并揭示其在填充因子ν=1时稳定陈数C=1的母态的关键作用。我们提出一种母态理论，认为陈绝缘体的稳定性及其空穴激发的平坦性是掺杂后获得FCIs的必要条件。随后我们进行多带精确对角化计算，以确认在莫尔电容效应存在时ν=2/3处FCIs的出现。我们的FCI态由带间涨落稳定，这与无莫尔势的情况不同，后者因带混合而崩溃。我们提供了对准样品中该态的首个一致理论，并解释了其在未对准样品中缺失的原因。
英文摘要：
While the necessity of a moiré potential for fractional Chern insulators (FCIs) in rhombohedral graphene-hBN superlattices, first predicted in Ref. 1, is now grounded in experiments, a theory of its origin and importance remains at large. We present a mechanism---the moiré capacitor effect---that enhances the moiré potential by electrostatically imprinting the valence charge density onto the conduction bands. We derive the analytical form of this term and reveal its crucial role in stabilizing a parent state with Chern number $C=1$ at filling $ν=1$. We propose a parent state theory which posits that stability of the Chern insulator and flatness of its hole excitations are necessary for obtaining FCIs upon doping. We then perform multi-band exact diagonalization calculations to confirm the emergence of FCIs at $ν= 2/3$ in the presence of the moiré capacitor effect. Our FCI state is stabilized by inter-band fluctuations, unlike in the moire-free case which collapses with band-mixing. We provide the first consistent theory for this state in aligned samples and explain its absence in unaligned ones.
