  Primordial black holes (PBHs) and the violation of the null energy condition
(NEC) have significant implications for our understanding of the very early
universe. We present a novel approach to generate PBHs via the NEC violation in
a single-field inflationary scenario. In our scenario, the universe transitions
from a first slow-roll inflation stage with a Hubble parameter $H =
H_{\text{inf}1}$ to a second slow-roll inflation stage with $H =
H_{\text{inf}2}\gg H_{\text{inf}1}$, passing through an intermediate stage of
NEC violation. The NEC violation naturally enhances the primordial scalar power
spectrum at a certain wavelength, leading to the production of PBHs with masses
and abundances of observational interest. We also investigate the
phenomenological signatures of scalar-induced gravitational waves (SIGWs)
resulting from the enhanced density perturbations. Our work highlights the
potential of utilizing a combination of PBHs, SIGWs, and primordial
gravitational waves as a valuable probe for studying NEC violation during
inflation, opening up new avenues for exploring the early universe.
