论文标题
偏置双层石墨烯中的动力筛选和激子结合状态
Dynamical screening and excitonic bound states in biased bilayer graphene
论文作者
论文摘要
激子绑定状态的特征是结合能$ε_b$和单粒子带隙$Δ_B$。这项工作为强（$ε_b\simδ_b$）和弱（$ε_b\llδ_b$）激发态绑定状态提供了理论描述，并特别应用于有偏的双层石墨烯。激子的标准描述基于波函数，该波函数由具有筛选有吸引力的电位的Schrödinger样方程确定。波函数方法仅在弱绑定式$ε_b\llδ_b$中有效。筛选取决于频率（动态筛选），这意味着迟钝。在具有强绑定的情况下，$ε_b\simδ_b$，由于延迟，无法进行波函数描述。取而代之的是，我们呼吁用电子孔绿色功能编写的伯特 - 盐分方程来解决问题。到目前为止，只有实验可以实现弱结合方案。我们的分析表明，强大的结合方案也是可能的，我们指定了可以在偏见双层石墨烯的原型典范中实现的条件。条件涉及偏见，门的配置和底物材料。为了验证我们的分析的准确性，我们将与弱结合方案的可用数据进行比较。我们预计将开发的动力筛选伯特盐盐技术应用于具有强结合的各种2D材料。
Excitonic bound states are characterised by a binding energy $ε_b$ and a single-particle band gap $Δ_b$. This work provides a theoretical description for both strong ($ε_b\simΔ_b$) and weak ($ε_b\llΔ_b$) excitonic bound states, with particular application to biased bilayer graphene. Standard description of excitons is based on a wave function that is determined by a Schrödinger-like equation with screened attractive potential. The wave function approach is valid only in the weak binding regime $ε_b\llΔ_b$. The screening depends on frequency (dynamical screening) and this implies retardation. In the case of strong binding, $ε_b\simΔ_b$, a wave function description is not possible due to the retardation. Instead we appeal to the Bethe-Salpeter equation, written in terms of the electron-hole Green's function, to solve the problem. So far only the weak binding regime has been achieved experimentally. Our analysis demonstrates that the strong binding regime is also possible and we specify conditions in which it can be achieved for the prototypical example of biased bilayer graphene. The conditions concern the bias, the configuration of gates, and the substrate material. To verify the accuracy of our analysis we compare with available data for the weak binding regime. We anticipate applying the developed dynamical screening Bethe-Salpeter techniques to various 2D materials with strong binding.
