We investigate the susceptibility of long-range ordered phases of two-dimensional dry aligning active matter to population and substrate spatial quenched disorder. The population disorder is taken in the form of a distribution of intrinsic individual chiralities. Using a combination of particle-level models and hydrodynamic theories derived from them, we show that while in finite systems all ordered phases resist a finite amount of such chirality disorder, the homogeneous ones (polar flocks and active nematics) are unstable to any amount of disorder in the infinite-size limit. For spatial quenched disorder, we find, for random couplings, the polar ordered phase remains long-range ordered, but qualitatively different from the pure (disorderless) case. For random scatters, polar order varies with system size but we find strong non-self-averaging, with sample-to-sample fluctuations dominating asymptotically, which prevents us from elucidating the asymptotic status of order. In summary quenched disorder affects active matter system in ways more complex and far reaching than heretofore believed, and polar order state is extremely fragile to such disorders.

施夏清，苏州大学特聘教授。南京大学物理系获得学士和博士学位。曾在香港浸会大学、法国原子能委员会、德国 Max-Planck 物理复杂系统研究所、美国卡弗里理论物理研究所进行学习和访问研究工作。长期关注于软物质物理和生物物理中非平衡体系的理论研究，尤其揭示了活性物质体系中奇异的非平衡动力学及临界行为的普适性机制，以及诸多活性实验体系中集体行为背后的统计动力学机制。