»ã±¨±êÌâ (Title)£ºQuantized vortex in an atomic Bose-Einstein condensate at Dirac point for honeycomb lattice(·äÎѾ§¸ñµÒÀ­¿Ëµã´¦Ô­×Ó²£É«-°®Òò˹̹Äý¾ÛÌåÖеÄÁ¿×Ó»¯ÎÐÐý)

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»ã±¨¹¦·ò (Time)£º2025Äê4ÔÂ17ÈÕ(ÖÜËÄ) 9:30

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When two or more energy bands become degenerate at a singular point in the momentum space, such singularity, or ¡°Dirac points¡±, gives rise to intriguing quantum phenomena as well as unusual material properties. Systems at the Dirac points can possess topological charges and their unique properties can be probed by various methods, such as transport measurement, interferometry and momentum spectroscopy. While the topology of Dirac point in the momentum space is well studied theoretically, observation of topological defects in a many-body quantum systems at Dirac point remain an elusive goal. Based on atomic Bose-Einstein condensate in a graphene-like optical honeycomb lattice, we directly observe emergence of quantized vortices at the Dirac point. The phase diagram of lattice bosons at the Dirac point is revealed. Our work provides a new way of generating vortices in a quantum gas, and the method is generic and can be applied to di?erent types of optical lattices with topological singularity, especially topological ?at band of twisted bilayer optical lattices.

References:

1£© Yunda Li, Wei Han, Zengming Meng, Wenxin Yang, Cheng Chin, Jing Zhang "Observation of quantized vortex in an atomic Bose-Einstein condensate at Dirac point"arXiv:2411.16287.

2£© Ce Wang, Chao Gao, Jing Zhang, Hui Zhai, Zhe-Yu Shi "Three-dimensional moir¨¦ crystal in ultracold atomic gases" Phys. Rev. Lett. 133, 163401 (2024).

3£© Zengming Meng, Liangwei Wang, Wei Han, Fangde Liu, Kai Wen, Chao Gao, Pengjun Wang, Cheng Chin, Jing Zhang "Atomic Bose-Einstein condensate in a twisted-bilayer optical lattice ¡°Nature 615, 231 (2023).