  The existence of Wigner crystallization, one of the most significant
hallmarks of strong electron correlations, has to date only been definitively
observed in two-dimensional systems. In one-dimensional (1D) quantum wires
Wigner crystals correspond to regularly spaced electrons; however, weakening
the confinement and allowing the electrons to relax in a second dimension is
predicted to lead to the formation of a new ground state constituting a zigzag
chain with nontrivial spin phases and properties. Here we report the
observation of such zigzag Wigner crystals by use of on-chip charge and spin
detectors employing electron focusing to image the charge density distribution
and probe their spin properties. This experiment demonstrates both the
structural and spin phase diagrams of the 1D Wigner crystallization. The
existence of zigzag spin chains and phases which can be electrically controlled
in semiconductor systems may open avenues for experimental studies of Wigner
crystals and their technological applications in spintronics and quantum
information.
