A Sigmoid-type memristor and its application in Hopfield neural network Yunzhen Zhang, Yunkai You, Xiaowei Yin, Yan Cao, Xiangqun Zhang, Weihua Xiong and Chengjie Chen Eur. Phys. J. Spec. Top., Publication ahead of print Published online: 09 July 2025 DOI: 10.1140/epjs/s11734-025-01784-9