石墨烯超晶格中不同载流子间干涉的光电指纹及其与扭曲石墨烯双层膜的类比
Optoelectronic Fingerprints of Interference between Different Charge Carriers in Graphene Superlattices and Analogies to Twisted Graphene Bilayers
摘要：
受最近关于Kekulé图案化石墨烯低能光谱的实验结果的启发，研究了具有空间调制的石墨烯超晶格的光电特征，该空间调制使单位晶格的尺寸增加了两倍，并将谷折叠到布里渊区的中心。对于像最近实验中看到的超晶格，光电响应揭示了多种载流子，它们的有效质量或费米速度不同。它们的特征类似于多重费米子系统，其中不同的频率间隔由不同类型的准粒子主导。值得注意的是，这些系统的响应表现出的光学电导率的特征峰，这表明一种不同种类的载体之间的干扰。我们还讨论了一个相关的超晶格，表现出合并狄拉克锥和能带平坦化，与哈密顿类似的扭曲双层石墨烯的手征模型的版本，其中长程莫尔调制已被取代的两个参数的偏置。
英文摘要：
Motivated by recent experimental findings on the low-energy spectrum of Kekulé-patterned graphene, the optoelectronic signatures of graphene superlattices with a spatial modulation that triples the size of the unit cell and folds the valleys to the center of the Brillouin zone are studied. For superlattices like those visualized in recent experiments, the optoelectronic response reveals multiple species of carriers distinguished by their effective masses or Fermi velocities. Their signatures are similar to those of systems hosting multifold fermions in which different frequency intervals are dominated by different types of quasiparticles. Remarkably, the response of these systems exhibits a characteristic peak in the optical conductivity suggesting a kind of interference between the different species of carriers. We also discuss a related superlattice that exhibits merging Dirac cones and band flattening, with a Hamiltonian that resembles a version of the chiral model for twisted bilayer graphene where the long-range moiré modulation has been substituted by a two-parameter bias.
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