Ni或Co与石墨或石墨烯密堆积表面界面处理想自旋过滤的理论预测
Theoretical prediction of perfect spin filtering at interfaces between close-packed surfaces of Ni or Co and graphite or graphene
摘要：
面心立方和六角密排面的面内晶格常数与石墨的面内晶格常数几乎完全匹配，因此它们共享一个共同的二维倒易空间。它们的电子结构是这样的，它们在一个自旋方向上在这个倒易空间中重叠，仅允许我们预测石墨与（111）fcc或（0001）hcp Ni或Co之间界面的完美自旋过滤。散射矩阵的第一性原理计算表明，自旋过滤对界面粗糙度和无序度的量非常不敏感，这些粗糙度和无序度显著影响自旋过滤。传统磁性隧道结或过渡金属与半导体之间的界面的过滤特性。当单个石墨烯片被吸附在这些开放的$d$ -壳过渡金属表面上时，其特征电子结构（在二维布里渊区中的K点处具有拓扑奇异性）被化学键合破坏。由于石墨烯仅弱键合到Cu，Cu在任一自旋的K点处的费米能处不具有状态，因此石墨烯的电子结构可以通过用一个或几个单层的Cu对Ni或Co进行除尘来恢复，同时仍然保持理想的自旋注入性质。
英文摘要：
The in-plane lattice constants of close-packed planes of fcc and hcp Ni and Co match that of graphite almost perfectly so that they share a common two dimensional reciprocal space. Their electronic structures are such that they overlap in this reciprocal space for one spin direction only allowing us to predict perfect spin filtering for interfaces between graphite and (111) fcc or (0001) hcp Ni or Co. First-principles calculations of the scattering matrix show that the spin filtering is quite insensitive to amounts of interface roughness and disorder which drastically influence the spin-filtering properties of conventional magnetic tunnel junctions or interfaces between transition metals and semiconductors. When a single graphene sheet is adsorbed on these open $d$-shell transition metal surfaces, its characteristic electronic structure, with topological singularities at the K points in the two dimensional Brillouin zone, is destroyed by the chemical bonding. Because graphene bonds only weakly to Cu which has no states at the Fermi energy at the K point for either spin, the electronic structure of graphene can be restored by dusting Ni or Co with one or a few monolayers of Cu while still preserving the ideal spin injection property.
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