  We investigate the amplification of curvature perturbations in a two-field
inflation model featuring a Gaussian potential bump. When the inflaton
encounters a potential bump along the inflationary trajectory, its rolling
speed is generally reduced, potentially causing a violation of the slow-roll
condition. Consequently, the original decaying modes of comoving curvature
perturbations during the slow-roll phase start growing, and lead to enhanced
small-scale density perturbations which can produce amounts of primordial black
holes (PBHs) and associated scalar-induced gravitational waves. In addition,
inflaton also undergoes sudden turnings at the encounter of the Gaussian
potential bump, which is insignificant to the overall curvature power spectrum
due to the short duration of these turns. Our paper offers a simple example of
the extension of a bump-like potential for PBH formation in a single-field
inflation to a two-field case, which helps alleviate the fine-tuning of initial
conditions to some extent.
