ARPES Signatures of Few-Layer Twistronic Graphenes.
ARPES Signatures of Few-Layer Twistronic Graphenes.
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DOI：
10.1021/acs.nanolett.3c01173
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发表时间：
2023-06-14
期刊：
影响因子：
10.8
通讯作者：
Wilson, Neil R. R.
中科院分区：
文献类型：
--
作者：
Nunn, James E. E.;McEllistrim, Andrew;Weston, Astrid;Garcia-Ruiz, Aitor;Watson, Matthew D. D.;Mucha-Kruczynski, Marcin;Cacho, Cephise;Gorbachev, Roman V. V.;Fal'ko, Vladimir I. I.;Wilson, Neil R. R.
在扭曲石墨烯层中观察到各种涌现的相关电子现象。许多电子结构预测已经被报道探索这个新领域，但很少有动量分辨电子结构测量来测试它们。我们使用角度分辨光发射光谱研究了扭曲双分子层、单分子层对双分子层和双分子层石墨烯（tDBG）的扭曲相关（1°< θ < 8°）能带结构。采用混合k·p模型对层间耦合进行了实验与理论的直接比较。在扭曲角度、堆叠几何形状和后门电压上发现了定量一致，验证了模型并揭示了扭曲石墨烯中的场致间隙。然而，对于θ = 1.5±0.2°，接近θ = 1.3°的tDBG，在费米能级附近发现了平坦带，测量带宽为Ew = 31±5 meV。对平带和下一个价带之间的间隙的分析表明，实验（Δh = 46±5 meV）和理论（Δh = 5 meV）之间存在偏差，表明在该体系中存在晶格弛豫。
Diverse emergent correlated electron phenomena have been observed in twisted-graphene layers. Many electronic structure predictions have been reported exploring this new field, but with few momentum-resolved electronic structure measurements to test them. We use angle-resolved photoemission spectroscopy to study the twist-dependent (1° < θ < 8°) band structure of twisted-bilayer, monolayer-on-bilayer, and double-bilayer graphene (tDBG). Direct comparison is made between experiment and theory, using a hybrid k·p model for interlayer coupling. Quantitative agreement is found across twist angles, stacking geometries, and back-gate voltages, validating the models and revealing field-induced gaps in twisted graphenes. However, for tDBG at θ = 1.5 ± 0.2°, close to the magic angle θ = 1.3°, a flat band is found near the Fermi level with measured bandwidth Ew = 31 ± 5 meV. An analysis of the gap between the flat band and the next valence band shows deviations between experiment (Δh = 46 ± 5 meV) and theory (Δh = 5 meV), indicative of lattice relaxation in this regime.
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