Jiade Li, Li Wang, Zhiyu Tao, Weiliang Zhong, Siwei Xue, Guangyao Miao, Weihua Wang, Jiandong Guo, Yani Wang, Zhibin Su, Hailin Peng, and Xuetao Zhu, Observation of the Nonanalytic Behavior of Optical Phonons in Monolayer Hexagonal Boron Nitride, NATURE COMMUNICATIONS 15, 1938 (2024)