Seminarium Fizyki Ciała Stałego

Gated multilayer graphene with rhombohedral stacking of layers exhibits a tunable energy gap. The stacking order can be changed when some layers are stretched, or delaminated and corrugated. In such cases, topological gapless states, connecting the valence and conduction band continua, appear at each valley. These states are localized at stacking domain walls (interfaces) that separate two different stacking orders. When the stacking change occurs along the zigzag direction, the Dirac cones at different valleys in the k-space are well separated. The gapless states are therefore valley-protected and provide one-dimensional and non-destructive valley currents that can flow along the stacking domain wall in opposite directions. Valley protection can be destroyed in the presence of atomic-scale defects. Here, we demonstrate the robustness of the gapless states to different defect-like perturbations of the multilayers. It is shown that some gapless states survive very strong distortions of the stacking domain walls. They persist when some layers are broken or partially removed, or even when vacancies or magnetic impurities are present at the stacking interface.