  Twisted graphene multilayers are highly tunable flatband systems for
developing new phases of matter. Thus far, while orbital ferromagnetism has
been observed in valley polarized phases, the long-range orders of other
correlated phases as well as the quantum phase transitions between different
orders mostly remain unknown. Here, we report an observation of Coulomb
interaction driven first-order quantum phase transitions and ferromagnetism in
twisted double bilayer graphene (TDBG). At zero magnetic field, the transitions
are revealed in a series of step-like abrupt resistance jumps with prominent
hysteresis loop when either the displacement field (D) or the carrier density
(n) is tuned across symmetry-breaking boundary near half filling, indicating a
formation of ordered domains. It is worth noting that the good turnability and
switching of these states gives a rise to a memory performance with a large
on/off ratio. Moreover, when both spin and valley play the roles at finite
magnetic field, we observe abundant first-order quantum phase transitions among
normal metallic states from charge neutral point, orbital ferromagnetic states
from quarter filling, and spin-polarized states from half filling. We interpret
these first-order phase transitions in the picture of phase separations and
spin domain percolations driven by multi-field tunable Coulomb interactions, in
agreement with Lifshitz transition from Hartree-Fock calculations. The observed
multi-filed tunable domain structure and its hysteresis resembles the
characteristics of multiferroics, revealing intriguing magnetoelectric
properties. Our result enriches the correlated phase diagram in TDBG for
discovering novel exotic phases and quantum phase transitions, and it would
benefit other twisted moir\'e systems as well.
