Intrinsic polar vortex crystals in A-site layer-ordered perovskites

Chao Xu^*, Nengneng Luo, Junyi Yue, Changsheng Chen, Tieyuan Bian, Chi Zhang, Xiangli Che, Jianwen Liang, Molly Meng-Jung Li, Jun Yin, Zhen Chen, Shujun Zhang, Xiaoqing Pan, Ye Zhu^*