Double-gradient seismic metamaterials with zero-frequency bandgap characteristic in a layered soil mediumNannan Shi, Han Liu, Lihui Wang, Jinbao Ji, Zhenbao Li, Shui Guo and Jian WangEPL, 144 2 (2023) 20001DOI: https://doi.org/10.1209/0295-5075/ad04ee