Spin multistability of cavity polaritons in a magnetic field

Ultrafast transitions between opposite-spin states of multicomponent bosonic condensates, proceeding on the timescale comparable to the lifetime of the particles the condensate consists of, are demonstrated in a resonantly excited system of cavity polaritons in a magnetic field. Spin-sensitive pair interactions enable fast and massive spin flips occurring at critical amplitudes due to the interplay between amplitude-dependent shifts of eigenstates and the Zeeman splitting. Dominant spin of a condensate can be toggled back and forth by tuning of the pump intensity only, which was impossible in spin-degenerate cavity-polariton systems, cavities with weak exciton-photon coupling, and other previously known photonic systems and devices.