  The system of cavity polaritons driven by a plane electromagnetic wave is
found to undergo the spontaneous breaking of spatial symmetry, which results in
a lifted phase locking with respect to the driving field and, consequently, in
the possibility of internal ordering. In particular, periodic spin and
intensity patterns arise in polariton wires; they exhibit strong long-range
order and can serve as media for signal transmission. Such patterns have the
properties of dynamical chimeras: they are formed spontaneously in perfectly
homogeneous media and can be partially chaotic. The reported new mechanism of
chimera formation requires neither time-delayed feedback loops nor non-local
interactions.
