Observing chiral edge states in gapped nanomechanical graphene

Edge states are an emerging concept in physics and have been explored as an efficient strategy to manipulate electrons, photons and phonons for next-generation hybrid electro-optomechanical circuits. Scientists have used gapless chiral edge states in graphene or graphene-like materials to understand exotic quantum phenomena such as quantum spin or valley Hall effects. In a new report now published on Science Advances, Xiang Xi and colleagues reported on experimental chiral edge states in gapped nanomechanical graphene; a honeycomb lattice of free-standing silicon nitride nanomechanical membranes with broken spatial inversion symmetry (presence of a dipole). The constructs were immune against backscattering in sharp bends and exhibited the valley-momentum locking effect. The team realized a smooth transition between the chiral edge states and the well-known valley kink states to open the door for experimental investigations of soft graphene-related physics in very-high-frequency, integrated nanomechanical systems.