二维ZrB2中的十二个不等Dirac锥
Twelve Inequivalent Dirac Cones in Two-Dimensional ZrB2
摘要：
在单层ZrB $_2$中费米能级附近存在12个不等价的狄拉克锥的理论证据。二维ZrB $_2$是一种机械稳定的d和p轨道化合物，具有独特的电子结构，具有来自不可约布里渊区高对称点的两个狄拉克锥，具有小的电子袋补偿。第一性原理计算表明，虽然一个锥是不敏感的晶格膨胀，第二锥消失的垂直Zr位置的小扰动。外部物理刺激下的内部对称破缺，以及SOC的相对论效应，能够选择性地去除狄拉克锥。一个合理的解释，在d-和p-轨道的混合，阐明了起源的狄拉克锥在一个平坦的结构中的罕见量。过渡金属d轨道的多功能性与B原子提供的蜂窝晶格相结合，产生了在二维材料中从未观察到的新特征。
英文摘要：
Theoretical evidence of the existence of 12 inequivalent Dirac cones at the vicinity of the Fermi energy in monolayered ZrB$_2$ is presented. Two-dimensional ZrB$_2$ is a mechanically stable d- and p-orbital compound exhibiting a unique electronic structure with two Dirac cones out of high-symmetry points in the irreducible Brillouin zone with a small electron-pocket compensation. First-principles calculations demonstrate that while one of the cones is insensitive to lattice expansion, the second cone vanishes for small perturbation of the vertical Zr position. Internal symmetry breaking with external physical stimuli, along with the relativistic effect of SOC, is able to remove selectively the Dirac cones. A rational explanation in terms of d- and p-orbital mixing is provided to elucidate the origin of the infrequent amount of Dirac cones in a flat structure. The versatility of transition metal d-orbitals combined with the honeycomb lattice provided by the B atoms yields novel features never observed in a two-dimensional material.
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