Quantized energy levels are one of the hallmarks of quantum mechanics at the atomic level. The manifestation of quantization in macroscopic physical systems has showcased important quantum phenomena, such as quantized conductance in (fractional) quantum Hall effects and quantized vortices in superconductors. Here we report the first experimental observation of quantized exciton energies in a macroscopic system with strong Coulomb interaction, monolayer WSe~crystal under a strong magnetic field. Employing helicity resolved magneto-reflectance spectroscopy, we observe a striking ladder of plateaus as a function of the gate voltage for both exciton resonance in one valley and exciton-polariton branch in the opposite valley, thanks to the inter-Landau levels (LLs) transitions governed by unique valley-selective selection rules. The observed quantized excitation energy level spacing sensitively depends on the doping level, indicating strong many-body effects. Our work will inspire the study of intriguing quantum phenomena originating from the interplay between LLs and many-body interactions in two-dimension monolayer crystals.} {I.

中文翻译：

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强磁场作用下单层WSe2中量化激子能量的观察

量子能级是原子级量子力学的标志之一。宏观物理系统中量化的表现已展示出重要的量子现象，例如（分数）量子霍尔效应中的量化电导和超导体中的量化涡旋。在这里，我们报告了在具有强库仑相互作用的宏观系统中，在强磁场下单层WSe〜晶体的激子能量量化的首次实验观察。利用螺旋解析磁反射光谱法，我们观察到高原的惊人阶梯作为一个谷的激子共振和相对谷的激子-极化子分支的栅极电压的函数，这要归功于Landau能级（LLs）的跃迁由独特的谷地选择规则控制。观察到的量化的激发能级间距敏感地取决于掺杂级，表明强烈的多体效应。我们的工作将激发对有趣的量子现象的研究，这些量子现象源于LL和二维单层晶体中多体相互作用之间的相互作用。