论文标题
石墨烯中单个空缺周围的局部多重组形成：基于Block-Lanczos DMRG方法的有效的Anderson模型分析
Local multiplet formation around a single vacancy in graphene: an effective Anderson model analysis based on the block-Lanczos DMRG method
论文作者
论文摘要
为了更好地理解石墨烯中单个空缺的电子结构，我们研究了有效的安德森模型的基态特性，该模型由周围空缺周围的周围碳原子的三个悬挂$ sp^2 $轨道组成，以及形成蜂窝状晶状体的碳原子的$π$轨道。采用块链球密度 - 矩阵重新归一化的方法，我们表明相关参数空间中有两个阶段，即弱耦合区域中的非磁相和现实参数区域中的自由磁矩相。系统分析发现，在自由磁矩阶段，在$ \ Mathcal {c} _3 $ point组中具有自旋1的$ \ Mathcal {C} _3 $ point 1的局部多重体在基态下占主导地位，并且该局部旋转1的大约一半是由电子在周围的$π$ orbital中筛选的，表明了$π$ orbit的范围，表明了均可启动的旋转型旋转旋转的旋转旋转旋转。此外，我们发现自由磁矩的出现是可抵抗载掺杂的稳健性，这与阿达托姆的石墨烯形成鲜明对比，从而解释了这两类系统中实验观察到的定性差异。我们还发现，与掺杂的情况相比，在空缺周围的$π$电子之间的自旋相关函数的增强，而在未居状的情况下，在未居状的情况下，自旋相关的函数的增强功能，而$ sp^2 $ gand的悬挂式的$σ$电子在空缺和$π$ undect and the proves and poct and poct and poct and poct and poct and poct and poct and dectuct and dectuct and dectuct and dect and dectuction中的旋转相关性功能仍然很大。因此，我们的计算在定性上支持了先前的实验，该实验表明具有两个不同起源的游离磁矩出现。
To better understand the electronic structure of a single vacancy in graphene, we study the ground state property of an effective Anderson model, consisting of three dangling $sp^2$ orbitals of the surrounding carbon atoms around the vacancy and the $π$ orbitals of carbon atoms that form the honeycomb lattice with a single vacancy. Employing the block-Lanczos density-matrix renormalization group method, we show that there are two phases in the relevant parameter space, i.e., a nonmagnetic phase in the weak coupling region and a free magnetic moment phase in the realistic parameter region. The systematic analysis finds that, in the free magnetic moment phase, local multiplets of the doubly degenerate irreducible representation of the $\mathcal{C}_3$ point group with spin 1 become dominant in the ground state, and approximately half of this local spin 1 is screened by electrons in the surrounding $π$ orbitals, indicating the emergence of the residual spin-1/2 free magnetic moment. Furthermore, we find that the emergence of the free magnetic moment is robust against carrier doping, which is in sharp contrast to the case of graphene with an adatom, thus explaining the qualitative difference observed experimentally in these two classes of systems. We also find the enhancement of the spin correlation function between $π$ electrons around the vacancy and those in the conduction band away from the vacancy in the undoped case, as compared to that in the doped case, while the spin correlation function between the $σ$ electrons in the $sp^2$ dangling orbitals around the vacancy and the $π$ electrons in the conduction band remains large in both undoped and doped cases. Our calculations thus support qualitatively the previous experiment that suggests the emergence of free magnetic moment with two distinct origins.
