We present a numerical study of exciton-polariton (polariton) condensation in a staggered polariton graphene showing a gapped $s$ band. The condensation occurs at the kinetically favorable negative mass extrema ($K$ and $K^{\prime }$ valleys) of the valence band. Considering attractive polariton-polariton interaction allows us to generate a spatially extended condensate. The symmetry breaking occurring during the condensate buildup leads to the formation of valley-polarized domains. This process can either be spontaneous, following the Kibble-Zurek scenario, or triggered, leading to a controlled spatial distribution of valley-polarized domains. The selection of a single valley breaks time-reversal symmetry, and the walls separating domains exhibit a reconfigurable topologically protected chiral current. This current emerges as a result of the interplay between the nontrivial valley topology and the condensation-induced symmetry breaking.

• Received 9 February 2022
• Accepted 12 July 2022

DOI:https://doi.org/10.1103/PhysRevLett.129.066802