  The competition between kinetic energy and Coulomb interactions in electronic
systems can lead to complex many-body ground states with competing
superconducting, charge density wave, and magnetic orders. Here we study the
low temperature phases of a strongly interacting zinc-oxide-based high mobility
two dimensional electron system that displays a tunable metal-insulator
transition. Through a comprehensive analysis of the dependence of electronic
transport on temperature, carrier density, in-plane and perpendicular magnetic
fields, and voltage bias, we provide evidence for the existence of competing
correlated metallic and insulating states with varying degrees of spin
polarization. Our system features an unprecedented level of agreement with the
state-of-the-art Quantum Monte Carlo phase diagram of the ideal jellium model,
including a Wigner crystallization transition at a value of the interaction
parameter $r_s\sim 30$ and the absence of a pure Stoner transition. In-plane
field dependence of transport reveals a new low temperature state with partial
spin polarization separating the spin unpolarized metal and the Wigner crystal,
which we examine against possible theoretical scenarios such as an
anti-ferromagnetic crystal, Coulomb induced micro-emulsions, and disorder
driven puddle formation.
