Chaotic motion of scalar particle coupling to Chern–Simons invariant in Kerr black hole spacetime Xuan Zhou, Songbai Chen and Jiliang Jing Eur. Phys. J. C, 81 3 (2021) 233 Published online: 16 March 2021 DOI: 10.1140/epjc/s10052-021-09042-7