  In the Randall-Sundrum (RS) II braneworld scenario, general relativity (GR)
is modified by adding an extra dimension such that it is indistinguishable from
GR in the weak gravity limit. However, such modifications may leave a mark in
the strong field regime. We therefore analyze massive scalar perturbations
around rotating black holes in the RS II model. Unlike black holes in GR, these
braneworld black holes carry a tidal charge that contains information about the
extra spatial dimension, and the rotation parameter for such black holes can
exceed unity. Through the method of continued fractions, we investigate the
quasinormal mode spectra, and the superradiant instabilities associated with
the existence of quasibound states, that is, gravitational atoms. In comparison
to the four-dimensional Kerr black hole, we report distinctive signatures of
the tidal charge and the rotation parameter, which manifest as signals of the
extra dimension, on both the fundamental quasinormal mode and the formation of
gravitational atoms. These findings offer insights into testing modifications
to GR and detecting ultralight bosonic particles around black holes.
