  We study the thermalization, after sudden and slow quenches, of an
interacting model having a quantum phase transition from a Sachdev-Ye-Kitaev
(SYK) non-Fermi liquid (NFL) to a Fermi liquid (FL). The model has SYK fermions
coupled to non-interacting lead fermions and can be realized in a graphene
flake connected to external leads. After a sudden quench to the NFL, a thermal
state is reached rapidly via collapse-revival oscillations of the quasiparticle
residue of the lead fermions. In contrast, the quench to the FL, across the
NFL-FL transition, leads to multiple prethermal regimes and much slower
thermalization. In the slow quench performed over a time $\tau$, we find that
the excitation energy generated has a remarkable intermediate-$\tau$
non-analytic power-law dependence, $\tau^{-\eta}$ with $\eta<1$, which
seemingly masks the dynamical manifestation of the initial residual entropy of
the SYK fermions. The power-law scaling is expected to eventually break down
for $\tau\to\infty$, signaling a violation of adiabaticity, due to the residual
entropy present in the SYK fermions.
