  The direct detection of cosmic neutrino background (CNB) has been a
longstanding challenge in particle physics, due to its low number density and
tiny neutrino masses. In this work, we consider the spectrum of the CNB boosted
by cosmic rays via the neutrino self-interaction, and calculate the event rate
of the boosted CNB-plasmon scattering in term of the dielectric response, which
accounts for in-medium screening effect of a condensed matter target. This can
be taken as the new direct detection strategy for the CNB in complementary to
the traditional one, which captures the CNB on a $\beta$-unstable nucleus. Our
result shows that one can either see the event of the CNB for the exposure of
per kg$\cdot$year, or puts a strong constraint on the neutrino
self-interaction. We further explore the background induced by the sub-MeV dark
matter and the boosted super-light dark matter.
