近日，美国加州大学圣巴巴拉分校Jin, Chenhao团队实现了扭曲WSe2中传播集体自旋谷模式的观测。相关论文于2026年5月7日发表在《自然—物理学》杂志上。
电荷中性集体模式的出现是关联量子相的一个标志性特征，但通常难以直接探测。在二维平带系统中，电荷响应已得到深入研究，但中性激发尚未被直接探测到。特别是，谷间相干态被认为是石墨烯基和半导体基体系中的一个统一主题，其特征是由于谷 U(1) 对称性自发破缺而产生中性戈德斯通模。然而，这一模式至今未被观测到。
研究组利用时空分辨超快成像技术，展示了扭曲 WSe2莫尔超晶格中的中性模式输运。他们发现了在范霍夫奇点附近出现的两种不同速度的传播集体模式。快速传播模式与谷间相干态的戈德斯通模相符，而慢速传播模式可能是一个有能隙的振幅模。它们可以理解为超流体集体模式在自旋-谷领域的类比。该研究为探测量子材料中的中性模式提供了一种强有力的方法，并为理解莫尔超晶格中电荷与自旋-谷物理之间的相互作用提供了关键见解。
附：英文原文
Title: Observation of propagating collective spin–valley modes in twisted WSe2
Author: Xiong, Richen, Guo, Yi, Qin, Chenxin, Wang, Taige, Yin, Fanzhao, Brantly, Samuel L., Choi, Youngjoon, Qi, Junhang, Zhou, Jinfei, Zhang, Zihan, Erdi, Melike, Watanabe, Kenji, Taniguchi, Takashi, Zhang, Shu, Tongay, Seth Ariel, Young, Andrea F., Fu, Liang, Jin, Chenhao
Issue&Volume: 2026-05-07
Abstract: The emergence of charge-neutral collective modes is a hallmark of correlated quantum phases but is often challenging to probe. In two-dimensional flatband systems, charge responses have been intensively investigated, but neutral excitations have not been directly probed. In particular, the intervalley-coherent state has been proposed as a unifying theme across graphene- and semiconductor-based systems and features a neutral Goldstone mode due to spontaneously broken valley U(1) symmetry. However, this mode has not been observed. Here we demonstrate the transport of neutral modes in twisted WSe2 moiré superlattices using a space-and-time-resolved ultrafast imaging technique. We show two propagating collective modes with different velocities that emerge near the Van Hove singularity. The fast-propagating mode is consistent with a Goldstone mode for an intervalley-coherent state, whereas the slow-moving mode is probably a gapped amplitude mode. They can be understood as the spin–valley analogues of the collective modes of a superfluid. Our study provides a powerful approach for probing neutral modes in quantum materials and offers key insights into the interplay between charge and spin–valley physics in moiré superlattices.
DOI: 10.1038/s41567-026-03280-w
Source: https://www.nature.com/articles/s41567-026-03280-w