Robust band gap and half-metallicity in graphene with triangular perforations
Robust band gap and half-metallicity in graphene with triangular perforations
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DOI：
10.1103/physrevb.93.245429
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发表时间：
2016-06-24
影响因子：
3.7
通讯作者：
Jauho, Antti-Pekka
中科院分区：
文献类型：
--
作者：
Gregersen, Soren Schou;Power, Stephen R.;Jauho, Antti-Pekka
预测理想的石墨烯反点阵在仔细指定的条件下显示出有希望的带隙行为（即E-G相似或等于500 meV）。然而，对于迄今为止所研究的结构，这种行为严重依赖于超晶格几何，并且在实验上对实际的失调不具有鲁棒性。本文研究了具有之字形边缘几何形状的矩形三角形反点阵列，并表明它们的带隙行为与标准带隙行为有质的不同，例如，由扶手椅边缘三角形组成的矩形阵列。在自旋非极化的情况下，与扶手椅边的反点相比，锯齿边的反点会产生更大的带隙，而不管扶手椅边的反点晶格中存在间隙的规则是什么。此外，在几何无序的情况下，锯齿边的对点比扶手椅边的对点显得更健壮。在平均场哈伯德方法中包含自旋极化，由于三角形几何施加的亚晶格不平衡，在每个反点处产生了很大的总体磁矩。半金属行为源于费米能量附近自旋分裂色散态的形成，与非极化情况相比，减少了带隙。这种行为也被发现在存在障碍时是稳健的。我们的研究结果强调了在石墨烯中使用三角形穿孔在具有实验实际无序水平的系统中打开电子带隙的可能性，此外，利用系统的强自旋依赖性用于自旋电子应用。
Ideal graphene antidot lattices are predicted to show promising band gap behavior (i.e., E-G similar or equal to 500 meV) under carefully specified conditions. However, for the structures studied so far this behavior is critically dependent on superlattice geometry and is not robust against experimentally realistic disorders. Here we study a rectangular array of triangular antidots with zigzag edge geometries and show that their band gap behavior qualitatively differs from the standard behavior which is exhibited, e.g., by rectangular arrays of armchair-edged triangles. In the spin unpolarized case, zigzag-edged antidots give rise to large band gaps compared to armchair-edged antidots, irrespective of the rules which govern the existence of gaps in armchair-edged antidot lattices. In addition the zigzag-edged antidots appear more robust than armchair-edged antidots in the presence of geometrical disorder. The inclusion of spin polarization within a mean-field Hubbard approach gives rise to a large overall magnetic moment at each antidot due to the sublattice imbalance imposed by the triangular geometry. Half-metallic behavior arises from the formation of spin-split dispersive states near the Fermi energy, reducing the band gaps compared to the unpolarized case. This behavior is also found to be robust in the presence of disorder. Our results highlight the possibilities of using triangular perforations in graphene to open electronic band gaps in systems with experimentally realistic levels of disorder, and furthermore, of exploiting the strong spin dependence of the system for spintronic applications.