论文标题

菱形三层石墨烯中的可调激子

Tunable Excitons in Rhombohedral Trilayer Graphene

论文作者

Quintela, M. F. C. Martins, Peres, N. M. R.

论文摘要

Trilayer石墨烯由于其堆栈依赖性磁电和光电特性而受到越来越多的关注,并且相对于单层和双层变体,其更强大的铁磁磁性。 此外,菱形堆积的三层石墨烯具有轻松通过垂直于层的外部电场或通过外部应变的施加缝隙的可能性。 在本文中,我们考虑一个外部电场来打开菱形三层石墨烯中的带隙,并研究系统的激子光学响应。 这是通过将紧密结合模型与伯特钙板方程的组合结合完成的,该方程是半分析的,仅需要简单的数值正交。 然后,我们讨论依赖山谷的光学选择规则,然后计算出在氮化硼中封装的菱形石墨烯三层烯类的情况下的激子线性光电电导率。 还讨论了通过外场的激子共振的可调性,以及随着场的增加,激子状态的定位越来越大。

Trilayer graphene is receiving an increasing level of attention due to its stacking--dependent magnetoelectric and optoelectric properties, and its more robust ferromagnetism relative to monolayer and bilayer variants. Additionally, rhombohedral stacked trilayer graphene presents the possibility of easily opening a gap via either an external electric field perpendicular to the layers, or via the application of external strain. In this paper, we consider an external electric field to open a bandgap in rhombohedral trilayer graphene and study the excitonic optical response of the system. This is done via the combination of a tight binding model with the Bethe--Salpeter equation, solved semi--analytically and requiring only a simple numerical quadrature. We then discuss the valley--dependent optical selection rules, followed by the computation of the excitonic linear optical conductivity for the case of a rhombohedral graphene trilayer encapsulated in hexagonal boron nitride. The tunability of the excitonic resonances via an external field is also discussed, together with the increasing localization of the excitonic states as the field increases.

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