Observation of valley-polarized topological phase transition in surface wave photonic crystals

Abstract

Simultaneous breaking of inversion symmetry and time-reversal symmetry brings topological phases fundamental in valleytronics, i.e. unpaired Dirac points and edge states. Here, we experimentally demonstrate the valley-polarized topological phase transition of these states. In a surface wave photonic crystal platform with honeycomb lattice, we use unequal metal pillars and magnetically biased gyromagnetic ferrite disks to modulate the breaking of symmetries. Switching of the unpaired Dirac points between K and K’ valleys is observed. More importantly, we realize valley manipulation of the edge states in heterojunctions constructed by specific topological phases. Our research thus paves the way for valley-polarized devices.