Numerous correlated many-body phases, both conventional and exotic, have been reported in magic-angle twisted bilayer graphene (MATBG)^{1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22,23,24}. However, the dynamics associated with these correlated states, crucial for understanding the underlying physics, remain unexplored. Here we combine exciton sensing and optical pump–probe spectroscopy to investigate the dynamics of isospin orders in MATBG with WSe₂ substrate across the entire flat band, achieving sub-picosecond resolution. We observe remarkably slow isospin dynamics in a broad filling range around ν = 2 and between ν = −3 and −2, with lifetimes of up to 300 ps that decouple from the much faster cooling of electronic temperature (about 10 ps). This non-thermal behaviour demonstrates the presence of abnormally long-lived modes in the isospin degrees of freedom. This observation, not anticipated by theory, implies the existence of long-range propagating collective modes, strong isospin fluctuations and memory effects and is probably associated with an intervalley coherent or incommensurate Kekulé spiral ground state. We further demonstrate non-equilibrium control of the isospin orders previously found around integer fillings. Specifically, through ultrafast manipulation, it can be transiently shifted away from integer fillings. Our study demonstrates a unique probe of collective excitations in MATBG and paves the way for actively controlling non-equilibrium phenomena in moiré systems.

魔角扭曲双层石墨烯 (MATBG) 中已报道了许多相关的多体相，包括传统的和奇异的相^{1,2,3,4,5,6,7,8,9,10,11,12,13 ,14,15,16,17,18,19,20,21,22,23,24} 。然而，与这些相关状态相关的动力学对于理解底层物理至关​​重要，仍未得到探索。在这里，我们结合激子传感和光学泵浦探针光谱来研究 MATBG 中与 WSe ₂衬底在整个平带上的同位旋级数的动态，实现亚皮秒分辨率。我们在ν = 2 附近以及ν = −3 和 −2 之间的宽填充范围内观察到非常缓慢的同位旋动力学，其寿命高达 300 ps，与电子温度更快的冷却（大约 10 ps）脱钩。这种非热行为表明同位旋自由度中存在异常长寿模式。这一观察结果并未被理论所预见，意味着存在远程传播集体模式、强烈的同位旋涨落和记忆效应，并且可能与层间相干或不相称的凯库勒螺旋基态有关。我们进一步证明了先前在整数填充周围发现的同位旋顺序的非平衡控制。具体来说，通过超快的操作，它可以暂时远离整数填充。我们的研究展示了 MATBG 中集体激发的独特探测，并为主动控制莫尔系统中的非平衡现象铺平了道路。