Comprehensive Electrostatic Modeling of Exposed Quantum Dots in Graphene/Hexagonal Boron Nitride Heterostructures

Eberth A. Quezada-López; Zhehao Ge; Takashi Taniguchi; Kenji Watanabe; Frédéric Joucken; Jairo Velasco

doi:10.3390/nano10061154

Article Comprehensive Electrostatic Modeling of Exposed Quantum Dots in Graphene/Hexagonal Boron Nitride Heterostructures

Eberth A. Quezada-López ; Zhehao Ge ; Takashi Taniguchi (National Institute for Materials Science) ; Kenji Watanabe (National Institute for Materials Science) ; Frédéric Joucken ; Jairo Velasco

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Eberth A. Quezada-López, Zhehao Ge, Takashi Taniguchi, Kenji Watanabe, Frédéric Joucken, Jairo Velasco. Comprehensive Electrostatic Modeling of Exposed Quantum Dots in Graphene/Hexagonal Boron Nitride Heterostructures. Nanomaterials. 2020, 10 (6), 1154. https://doi.org/10.3390/nano10061154

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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). Spectroscopic characterization of these exposed QDs with the scanning tunneling microscope (STM) have 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.

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