Author(s): Yajun Zhang, Devesh R. Kripalani, Xu He, Konstantin Shapovalov, Jiyuan Yang, Hongjian Zhao, Shi Liu, Huadong Yong, Xingyi Zhang, Jie Wang, Kun Zhou, and Philippe Ghosez Spin density waves (SDWs) represent a fundamental paradigm of spatially modulated order in condensed matter systems, yet their electrical and mechanical analogs—polarization and strain density waves (PDWs and StDWs)—have remained elusive as equilibrium phases. Here, we introduce a general, symmetry-… [Phys. Rev. Lett. 137, 086101] Published Tue Aug 18, 2026