Tetraquark state X(6900) and the interaction between diquark and antidiquark Hong-Wei Ke, Xin Han, Xiao-Hai Liu and Yan-Liang Shi Eur. Phys. J. C, 81 5 (2021) 427 Published online: 17 May 2021 DOI: 10.1140/epjc/s10052-021-09229-y