乔振华 教授
中国科技大学物理系
时 间： 11月19日下午4:00点
地 点： 唐楼A313
Abstract: In addition to real spin, sublattices and valleys are another two important degrees of freedom in graphene systems. When the inversion symmetry is broken by applying a staggered sublattice potential in graphene, a bulk band gap opens to support a quantum valley Hall effect, where valleys are decoupled. If the applied potential varies spatially, a chorally propagating zero-line mode is produced and shown to exhibit novel transport properties. When valleys become coupled in specific super-cells due to the periodic adsorption, inter valley coupling plays a role to tune the valley polarization, which is necessary in engineering valleytronics. We give a theory to explain the physical origin of inter valley scattering and find a new metallic phase with single quadratically touched Dirac-cone. We also show that the randomization of adsorption positions can greatly decrease the inter valley scattering.