Stability of charged black holes in string theory under charged massive scalar perturbations

Similar to the superradiant effect in Reissner-Nordstrom black holes, a charged scalar field can be amplified when impinging on the charged black hole in string theory. According to the black-hole bomb mechanism, the mass term of the incident field can work as the reflecting mirror, which may trigger the instability of the black hole. We study the possible instability triggered by superradiant effects and demonstrate that the charged black hole in string theory is stable against the massive charged scalar perturbation. The reason is that there is no trapping potential well in the black hole exterior, which is separated from the horizon by a potential barrier, and there are no bound states in the superradiant regime.