AI 中文总结
本研究开发毫开尔文远红外平台，观测到魔角双层石墨烯平带电子的远红外共振，揭示轻-重费米子杂化的关键对称性，为理解该体系光-物质相互作用提供基础。
AI 中文摘要
莫尔工程在扭曲二维（2D）材料中可从根本上改变低能带、相互作用及拓扑量子态。尽管已有大量研究，但由于极端实验挑战，特征远红外（FIR）区域中相互作用莫尔能带的光学光谱学仍在很大程度上未被探索。我们利用新开发的毫开尔文FIR平台，报道了在魔角双层石墨烯（MATBG）中观测到长期寻求的平带电子特征FIR共振。我们观测到构成MATBG平带的轻、重费米子的高度可调光谱特征。利用拓扑重费米子模型（THF），我们证明巡游拓扑电子充当与光场强耦合的“天线”，其共振频率因与局域重电子的杂化而重整化。我们建立了MATBG的光学选择定则，揭示了控制轻-重费米子杂化的关键对称性。在电中性时，我们观测到低于在位库仑能的显著共振，意味着新多体模式的出现。我们的实验和模型为理解MATBG中的光-物质相互作用提供了基础，并实现了低至毫开尔文温度下莫尔能带的共振光学光谱学。
英文摘要
Moiré engineering in twisted two-dimensional (2D) materials radically alters low-energy bands, interactions and topological quantum states. Despite extensive studies, optical spectroscopy of interacting moiré bands in the characteristic far-infrared (FIR) regime has remained largely unexplored due to extreme experimental challenges. Using a newly developed millikelvin FIR platform, we report the observation of the long-sought-after characteristic FIR resonances of flat-band electrons in magic-angle twisted bilayer graphene (MATBG). We observe highly tunable spectroscopic signatures of interacting light and heavy fermions that constitute the flat bands in MATBG. Using the topological heavy-fermion model (THF), we show that itinerant topological electrons act as an "antenna" that couples strongly to the optical field, with resonant frequencies renormalized by the hybridization with localized heavy electrons. We establish optical selection rules of MATBG which uncovers the key symmetry governing light-heavy fermion hybridization. At charge neutrality, we observe pronounced resonances at energies below the on-site Coulomb energy, implying the emergence of new many-body modes. Our experiments and modeling provide a fundamental understanding of light-matter interactions in MATBG and enable resonant optical spectroscopy of moiré bands down to millikelvin temperatures.
Comments52 pages in total, incluidng 25 pages on main text, figures and extended figures + tables, and 30 pages on theory supplementary information
