  We study the prethermal dynamics of the Gross-Neveu-Yukawa quantum field
theory, suddenly quenched in the vicinity of a quantum critical point. We find
that the universal prethermal dynamics is controlled by two fixed points
depending on the size of the quench. Besides the usual equilibrium chiral Ising
fixed point for a shallow quench, a dynamical chiral Ising fixed point is
identified for a deep quench. Intriguingly, the latter is a non-thermal fixed
point without any equilibrium counterpart due to the participation of gapless
fermionic fields. We also find that in the scaling regime controlled by the
equilibrium fixed point, the initial slip exponent is rendered negative if
there are enough flavors of fermions, thus providing a unique signature of
fermionic prethermal dynamics. We then explore the temporal crossover between
the universal scaling regimes governed by the two universality classes.
Possible experimental realizations are also discussed.
