Quantum confinement, the restriction of electron movement to specific regions, significantly impacts material properties. This study investigates the role of quantum confinement in the recently discovered kagome superconductors CsV₃Sb₅. Combining angle-resolved photoemission spectroscopy (ARPES) and density-functional theory (DFT) simulations, we reveal the formation of two-dimensional quantum well states due to confinement of bulk electron pockets and Dirac cones to the surface layer. Calculations confirm that the ARPES spectra originate primarily from the top two layers. These results reconcile discrepancies between previous experimental and theoretical band structures and highlight the importance of quantum confinement, along with strong correlation and band topology, in shaping the material's electronic properties.

Yongqing Cai, Yuan Wang, Zhanyang Hao, Yixuan Liu, Xuelei Sui, Zuowei Liang, Xiao-Ming Ma, Fayuan Zhang, Zecheng Shen, Chengcheng Zhang, Zhicheng Jiang, Yichen Yang, Wanling Liu, Qi Jiang, Zhengtai Liu, Mao Ye, Dawei Shen, Han Gao, Hanbo Xiao, Zhongkai Liu, Zhe Sun, Yi Liu, Shengtao Cui, Jiabin Chen, Le Wang, Cai Liu, Junhao Lin, Bing Huang, Zhenyu Wang, Xianhui Chen, Jia-Wei Mei, Jianfeng Wang, Chaoyu Chen