Mixed state entanglement for holographic axion model Yi-fei Huang, Zi-jian Shi, Chao Niu, Cheng-yong Zhang and Peng Liu Eur. Phys. J. C, 80 5 (2020) 426 Published online: 15 May 2020 DOI: 10.1140/epjc/s10052-020-7921-y