Having previously been the subject of decades of semiconductor research, cadmium arsenide (${\mathrm{Cd}}_3{\mathrm{As}}_2$) has now reemerged as a topological material, realizing ideal three-dimensional Dirac points at the Fermi level. These topological Dirac points lead to a number of extraordinary transport phenomena, including strong quantum oscillations, large magnetoresistance, ultrahigh mobilities, and Fermi velocities exceeding graphene. The large mobilities persist even in thin films and nanowires of ${\mathrm{Cd}}_3{\mathrm{As}}_2,$ suggesting the involvement of topological surface states. However, computational studies of the surface states in this material are lacking, in part due to the large 80-atom unit cell. Here we present the computed Fermi-arc surface states of a ${\mathrm{Cd}}_3{\mathrm{As}}_2$ thin film, based on a tight-binding model derived directly from the electronic structure. We show that despite the close proximity of the Dirac points, the Fermi arcs are very long and straight, extending through nearly the entire Brillouin zone. The shape and spin properties of the Fermi arcs suppress both back- and side scattering at the surface, which we show by explicit integrals over the phase space. The introduction of a small symmetry-breaking term, expected in a strong electric field, gaps the electronic structure, creating a weak topological insulator phase that exhibits similar transport properties. Crucially, the mechanisms suppressing scattering in this material differ from those in other topological materials such as Weyl semimetals and topological insulators, suggesting a new route for engineering high-mobility devices based on Dirac semimetal surface states.

中文翻译：

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拓扑狄拉克半金属 Cd3As2 的费米弧介导的电导率不存在反向散射

砷化镉曾是数十年半导体研究的主题（${\mathrm{光盘}}_3{\mathrm{作为}}_2$）现已作为拓扑材料重新出现，在费米能级实现了理想的三维狄拉克点。这些拓扑狄拉克点导致了许多非凡的输运现象，包括强量子振荡、大磁阻、超高迁移率和超过石墨烯的费米速度。即使在薄膜和纳米线中，大的迁移率仍然存在${\mathrm{光盘}}_3{\mathrm{作为}}_2,$表明拓扑表面态的参与。然而，由于该材料具有 80 个原子的大晶胞，因此缺乏对该材料表面态的计算研究。在这里，我们提出了计算的费米弧表面态${\mathrm{光盘}}_3{\mathrm{作为}}_2$薄膜，基于直接源自电子结构的紧束缚模型。我们表明，尽管狄拉克点非常接近，但费米弧非常长且直，几乎延伸穿过整个布里渊区。费米弧的形状和自旋特性抑制了表面的反向和侧向散射，我们通过相空间上的显式积分来证明这一点。引入一个小的对称破缺项（预计在强电场中）会在电子结构中产生间隙，从而产生表现出类似输运特性的弱拓扑绝缘体相。至关重要的是，这种材料中抑制散射的机制与其他拓扑材料（例如外尔半金属和拓扑绝缘体）不同，这为设计基于狄拉克半金属表面态的高迁移率器件提供了一条新途径。