  Superradiant clouds may develop around a rotating black hole, if there is a
bosonic field with Compton wavelength comparable to the size of the black hole.
In this paper, we investigate the effects of the cloud on the orbits of nearby
compact objects. In particular, we consider the dynamical friction and the
backreaction due to level mixing. Under these interactions, the probability of
a black hole dynamically capturing other compact objects, such as stellar mass
black holes and neutron stars, is generally enhanced with the presence of the
cloud. For extreme mass ratio inspirals and binary stellar mass binary black
holes, the cloud-induced orbital modulation may be detected by observing the
gravitational waveform using space borne gravitational wave detectors, such as
LISA. Interestingly within certain range of boson Compton wavelength, the
enhanced capture rate of stellar mass black holes could accelerate hierarchical
mergers, with higher-generation merger product being more massive than the mass
threshold predicted by supernova pair instability. These observational
signatures provide promising ways of searching light bosons with gravitational
waves.
