石墨烯能带中的重叠矩阵效应:Tight-Binding方法在模拟中的研究

采用紧束缚方法计算了石墨烯的价带(π)和导带(π*),考虑了非正交基矢下重叠矩阵效应,重叠积分参量s越小,导带越靠近费米面,而价带越远离费米面.在重叠积分参量s≤0.1时,基本保持了原子在实际空间中重叠所引起的能带的改变,太大(s=0.4)则会导致物理上失效.计算了石墨烯的能态密度,在费米面ε=0处(对应Dirac点)的能态密度为零,并且在Dirac点附近呈线性变化.

The overlap matrix effect in graphene band structure: A theoretical investigation of tight-binding method

By employing the tight-binding method, we calculated the valence band and the conduction band of grapheme. Under the consideration of the overlap matrix effect in the case of nonorthogonal basis, when the overlap integral parameter s decreases, the conduction band gets closer to the Fermi surface and the valence band becomes further to the Fermi surface. When the parameter s is smaller than 0.1, it almost keeps the change of energy band induced by the atoms in real space. If s becomes larger, such as, s=0.4, the energy band is totally distorted and leads to the unphysical phenomenon. Moreover, we have calculated the density of states of grapheme. On the Fermi surface (Dirac point), the density of states is zero, and we also observed a linear variation around the Dirac point.