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Observation of Dirac bands in artificial graphene in small-period nanopatterned GaAs quantum wells
Nature Nanotechnology ( IF 38.3 ) Pub Date : 2017-11-27 , DOI: 10.1038/s41565-017-0006-x
Sheng Wang,Diego Scarabelli,Lingjie Du,Yuliya Y. Kuznetsova,Loren N. Pfeiffer,Ken W. West,Geoff C. Gardner,Michael J. Manfra,Vittorio Pellegrini,Shalom J. Wind,Aron Pinczuk

Charge carriers in graphene behave like massless Dirac fermions (MDFs) with linear energy-momentum dispersion1, 2, providing a condensed-matter platform for studying quasiparticles with relativistic-like features. Artificial graphene (AG)—a structure with an artificial honeycomb lattice—exhibits novel phenomena due to the tunable interplay between topology and quasiparticle interactions3,4,5,6. So far, the emergence of a Dirac band structure supporting MDFs has been observed in AG using molecular5, atomic6, 7 and photonic systems8,9,10, including those with semiconductor microcavities11. Here, we report the realization of an AG that has a band structure with vanishing density of states consistent with the presence of MDFs. This observation is enabled by a very small lattice constant (a = 50 nm) of the nanofabricated AG patterns superimposed on a two-dimensional electron gas hosted by a high-quality GaAs quantum well. Resonant inelastic light-scattering spectra reveal low-lying transitions that are not present in the unpatterned GaAs quantum well. These excitations reveal the energy dependence of the joint density of states for AG band transitions. Fermi level tuning through the Dirac point results in a collapse of the density of states at low transition energy, suggesting the emergence of the MDF linear dispersion in the AG.

中文翻译:

小周期纳米图形GaAs量子阱中人造石墨烯的狄拉克谱带的观察

石墨烯中的载流子的行为类似于具有线性能量动量色散1、2的无质量狄拉克费米子(MDF),为研究具有相对论性特征的准粒子提供了一个凝聚态平台。人造石墨烯(AG)是一种具有人造蜂窝状晶格的结构,由于拓扑结构和准粒子相互作用3、4、5、6之间的可调相互作用,因此表现出新颖的现象。到目前为止,已经在AG中观察到了支持MDF的Dirac能带结构的出现,其中使用了分子5,原子6,7和光子系统8,9,10,包括那些具有半导体微腔的系统11。。在这里,我们报告了具有带结构的AG的实现,该带结构的消失密度与MDF的存在一致。 纳米制造的AG图案的极小的晶格常数(a = 50 nm)叠加在高质量GaAs量子阱所承载的二维电子气上,从而实现了这一观察。共振非弹性光散射光谱显示出低层跃迁,这种跃迁未出现在未构图的GaAs量子阱中。这些激发揭示了AG带跃迁的状态的联合密度的能量依赖性。通过狄拉克点进行的费米能级调谐会导致在低跃迁能量下状态密度崩溃,这表明在AG中出现了MDF线性色散。
更新日期:2017-11-28
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