Superradiant stability of five and six-dimensional extremal Reissner–Nordstrom black holes Jia-Hui Huang, Tian-Tian Cao and Mu-Zi Zhang Eur. Phys. J. C, 81 10 (2021) 904 Published online: 13 October 2021 DOI: 10.1140/epjc/s10052-021-09715-3