Comprehensive Electrostatic Modeling of Exposed Quantum Dots in Graphene/Hexagonal Boron Nitride Heterostructures
Comprehensive Electrostatic Modeling of Exposed Quantum Dots in Graphene/Hexagonal Boron Nitride Heterostructures
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DOI：
10.3390/nano10061154
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发表时间：
2020-06
期刊：
影响因子：
5.3
通讯作者：
E. Quezada-López;Zhehao Ge;T. Taniguchi;Kenji Watanabe;F. Joucken;J. Velasco
中科院分区：
文献类型：
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作者：
E. Quezada-López;Zhehao Ge;T. Taniguchi;Kenji Watanabe;F. Joucken;J. Velasco
最近的实验进展已经使得能够在石墨烯/六方氮化硼（hBN）异质结构中产生可调的局部静电势，而不隐藏石墨烯表面。这些电势限制了石墨烯电子，产生了类似于静电定义的量子点（QD）的系统。用扫描隧道显微镜（STM）对这些暴露的量子点进行光谱表征，发现了与穿过量子点壁的100%隧穿概率一致的有趣的共振。这种效应被称为克莱因隧道效应，是相对论粒子的象征，强调了这些石墨烯量子点的独特性。尽管静电定义的石墨烯量子点的进步，其光谱特征的完整理解仍然是难以捉摸的。在这项研究中，我们通过全面考虑暴露的石墨烯量子点的静电环境来解决这一知识失误。然后，我们将这些考虑因素应用到紧束缚计算中，以模拟石墨烯量子点的局域态密度。我们发现，列入STM尖端的静电与基础hBN收费再现所有的实验解决的光谱特征。我们的工作提供了一个有效的方法来模拟暴露的石墨烯量子点的静电。这里讨论的方法可以应用于其他静电定义的量子点系统，也暴露。
Recent experimental advancements have enabled the creation of tunable localized electrostatic potentials in graphene/hexagonal boron nitride (hBN) heterostructures without concealing the graphene surface. These potentials corral graphene electrons yielding systems akin to electrostatically defined quantum dots (QDs). The spectroscopic characterization of these exposed QDs with the scanning tunneling microscope (STM) revealed intriguing resonances that are consistent with a tunneling probability of 100% across the QD walls. This effect, known as Klein tunneling, is emblematic of relativistic particles, underscoring the uniqueness of these graphene QDs. Despite the advancements with electrostatically defined graphene QDs, a complete understanding of their spectroscopic features still remains elusive. In this study, we address this lapse in knowledge by comprehensively considering the electrostatic environment of exposed graphene QDs. We then implement these considerations into tight binding calculations to enable simulations of the graphene QD local density of states. We find that the inclusion of the STM tip’s electrostatics in conjunction with that of the underlying hBN charges reproduces all of the experimentally resolved spectroscopic features. Our work provides an effective approach for modeling the electrostatics of exposed graphene QDs. The methods discussed here can be applied to other electrostatically defined QD systems that are also exposed.