Correlated Electron Research Group (CERG), RIKEN-ASI, Wako, Saitama 351-0198, Japan.
Nat Commun. 2012 Feb 14;3:679. doi: 10.1038/ncomms1679.
The spin-orbit interaction affects the electronic structure of solids in various ways. Topological insulators are one example in which the spin-orbit interaction leads the bulk bands to have a non-trivial topology, observable as gapless surface or edge states. Another example is the Rashba effect, which lifts the electron-spin degeneracy as a consequence of the spin-orbit interaction under broken inversion symmetry. It is of particular importance to know how these two effects, that is, the non-trivial topology of electronic states and the Rashba spin splitting, interplay with each other. Here we show through sophisticated first-principles calculations that BiTeI, a giant bulk Rashba semiconductor, turns into a topological insulator under a reasonable pressure. This material is shown to exhibit several unique features, such as a highly pressure-tunable giant Rashba spin splitting, an unusual pressure-induced quantum phase transition, and more importantly, the formation of strikingly different Dirac surface states at opposite sides of the material.
自旋轨道相互作用以各种方式影响固体的电子结构。拓扑绝缘体就是一个例子，其中自旋轨道相互作用导致体带具有非平凡的拓扑，可以观察到无带隙的表面或边缘态。另一个例子是 Rashba 效应，由于自旋轨道相互作用在破坏的反转对称性下，导致电子自旋简并度被解除。特别重要的是要知道这两种效应，即电子态的非平凡拓扑和 Rashba 自旋劈裂，是如何相互作用的。在这里，我们通过复杂的第一性原理计算表明，BiTeI，一种巨大的体 Rashba 半导体，在合理的压力下变成拓扑绝缘体。该材料表现出多种独特的性质，例如高度可调节的巨大 Rashba 自旋劈裂、不寻常的压力诱导量子相变，更重要的是，在材料的相对侧形成了明显不同的狄拉克表面态。
