石墨烯纳米环的电子结构和持续电流 Electronic Structure and Persistent Current in Graphene Rings

基于紧束缚理论，研究了石墨烯纳米环的电子结构和磁响应特性。计算结果表明当存在垂直磁场时，由于谷间散射,能谱中每个能带由六条能级组成。根据环的电子结构，石墨烯纳米环可以分为金属环和半导体环。在金属环中，持续电流随着磁通增大呈现线性变化关系。然而，半导体环的持续电流随着磁通增大呈现正弦函数关系。无论是金属还是半导体石墨烯环，磁通驱动下的电子都沿着环做逆时针运动，因而呈现出抗磁特性。 The electronic structure and persistent current of graphene rings have been studied using the tight-binding model. Our results show that in the presence of a perpendicular magnetic field, en-ergy spectrum can be grouped into bands with six levels per band owing to inter-valley scattering. According to degeneracy of energy level at the Fermi energy, the graphene rings are divided into two groups, metallic and semiconducting rings. In metallic rings, the persistent current within a flux period changes linearly with magnetic flux ϕ, while it is a sinusoidal periodical function of ϕ in semiconducting rings. Both metallic and semiconducting rings exhibit diamagnetic response, because the electrons driven by magnetic flux flow anticlockwise along the rings.