二维材料及异质结具有丰富的物理特性和广泛的应用前景，其能带结构、多体相互作用以及非平衡态超快动力学过程对于揭示其物理特性及实现物态调控具有重要的科学意义。本文利用角分辨光电子能谱 (ARPES)、超快时间分辨角分辨光电子能谱 (Tr-ARPES) 和具有百纳米光斑的角分辨光电子能谱（Nano-ARPES），针对石墨烯/氮化硼异质结和锂插层石墨烯的电子结构、电子-电子及电子-声子等多体相互作用及非平衡态超快动力学开展研究，取得以下创新性研究成果：（1）通过结合 ARPES 和原位电子掺杂，首次在典型范德华异质结石墨烯/氮化硼中观测到电子-等离激元相互作用产生的等离极化子对电子结构的重整，并提取出可用于表征电子-电子相互作用强度的有效精细常数。与其它衬底上的石墨烯相比，石墨烯/氮化硼异质结具有较大的有效精细常数，表明氮化硼衬底对于增强异质结体系中电子-电子相互作用起着关键的作用。（2）通过 Li 插层石墨烯，引入了具有 (√3×√3)?30° 周期调制的凯库勒 (Kekulé)序，使 K 和K′ 两个能谷具有不同手性的狄拉克锥被复制到Γ 点且发生耦合，并且从狄拉克锥处能隙的打开、实空间具有 Kekulé-O 构型的电子态以及能隙附近手征对称性的混合三个方面提供了手征对称性破缺的实验证据。该结果不仅在真实材料体系中实现了可类比于标准模型中基本粒子质量起源的手征对称性破缺，还为进一步研究手征对称性破缺相关的新奇物理效应提供了可能。（3）首次利用高能量和动量分辨率的Tr-ARPES 捕捉到凯库勒石墨烯在脉冲激光激发后的电子结构及电子-声子耦合作用导致的自能的超快动态演化过程，并且揭示了声子的能量阈值效，即与电子显著耦合的两个声子模式划分了电子弛豫的几个能量窗口，不同能量区间的电子具有显著不同的弛豫时间。该工作通过直接的超快时间分辨自能探测及能量分辨的电子弛豫时间探测，首次揭示了特定模式的声子及相应的电子-声子耦合在电子弛豫中所起的主导作用。本文的研究结果揭示了石墨烯/氮化硼异质结和凯库勒石墨烯中丰富的电子结构、多体相互作用和多体相互作用的动态过程，以及层间相互作用对过渡金属硫族化合物能带结构的影响，为更好地理解二维体系中多体相互作用的微观机制提供了重要的信息。
Two-dimensional materials and heterostructures exhibit rich physical properties and potential applications. Revealing their electronic structure, many-body interactions and non-equilibrium ultrafast dynamics are critical for understanding the underlying physics and manipulating their physical properties. In this thesis, we utilize angle-resolved photoemission spectroscopy (ARPES), time- and angle-resolved photoemission spectroscopy (Tr-ARPES) and nano-spot angle-resolved photoemission spectroscopy (Nano-ARPES) to investigate the electronic structure, many-body interactions including electron-electron,electron-phonon interaction, and the non-equilibrium ultrafast dynamics of graphene/hBN and Li-intercalated graphene. Major scientific achievements are shown as follows:(1) By combining ARPES with in situ electron doping, we report the first observation of electron-plasmon coupling induced plasmarons and band renormalization in the model heterostructure of graphene/h-BN. The band renormalization leads to a diamond-shaped electronic structure at the Dirac point, from which we can extract the effective fine structure constant which defines the electron-electron interaction strength. Compared with graphene placed on other substrates, the effective fine structure constant of graphene on the h-BN substrate is the largest, indicating the important role of h-BN substrate in enhancing the electron-electron interaction in heterostructures.(2) By Li intercalation, we introduce a Kekulé order with (√3×√3)?30° period into graphene, which folds the Dirac cones from K and K′ valleys to the Γ point and enables coupling between Dirac cones with opposite chiralities. By combining the gap opening at the Dirac point, the Kekué-O type modulation in the topography, and the chirality mixing near the gap edge, we provide direct experimental evidence of the chiral symmetry breaking (CSB). Our results not only realize the CSB in a real material, which is analogous to the dynamical mass generation in particle physics, but also provide new opportunities for exploring CSB related intriguing physics.(3) We report the first experimental observation of ultrafast dynamics of the electronic structure and electron-phonon induced dynamical evolution of the self-energy in the Kekulé-ordered graphene by Tr-ARPES with high energy and momentum resolution. Moreover, we reveal the phonon threshold effect, in which two strongly coupled phonon modes set energy windows for the electron relaxation, and electrons show different relaxation times in those different energy windows. By directly detecting the ultrafast selfenergy dynamics and the energy-resolved electron relaxation time, our work reveals the dominant role of mode-specific phonons and electron-phonon coupling in determining the electron relaxation process for the first time.This thesis reveals the rich electronic structure, many-body interactions, and nonequilibrium many-body interaction dynamics in graphene/h-BN heterostructure and the Kekulé-ordered graphene, as well as the influence of the interlayer coupling on the band structure of transition metal dichalcogenides, thereby providing important insights for understanding the microscopic mechanism of many-body interactions.
