When two dimensional crystals are atomically close, their finite thickness becomes relevant. Using transport measurements, we investigate the electrostatics of two graphene layers, twisted by θ = 22° such that the layers are decoupled by the huge momentum mismatch between the K and K′ points of the two layers. We observe a splitting of the zero-density lines of the two layers with increasing interlayer energy difference. This splitting is given by the ratio of single-layer quantum capacitance over interlayer capacitance C subm/sub and is therefore suited to extract C subm/sub. We explain the large observed value of C subm/sub by considering the finite dielectric thickness d subg/sub of each graphene layer and determine d subg/sub ≈ 2.6 ?. In a second experiment, we map out the entire density range with a Fabry-Pérot resonator. We can precisely measure the Fermi wavelength λ in each layer, showing that the layers are decoupled. Our findings are reproduced using tight-binding calculations.
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机译:当二维晶体是原子上关闭时,它们的有限厚度变得相关。使用运输测量,我们研究了两个石墨烯层的静电,θ= 22°扭曲,使得层通过两层的K和K'点之间的巨大动量失配。我们观察两层的零密度线的分裂随着层间能量差的增加。该分裂由单层量子电容在层间电容C m sub上的比率给出,因此适于提取C m sub>。通过考虑每个石墨烯层的有限介电厚度D g sub>来解释C m sub>的大的观察值。在第二个实验中,我们用法布里 - Péroot谐振器映射整个密度范围。我们可以精确地测量每层的FERMI波长λ,表明层分离。我们的研究结果使用紧密结合计算来复制。
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