Department of Materials Science and Engineering, University of Utah, Salt Lake City, Utah 84112, USA.
Nat Commun. 2013;4:1384. doi: 10.1038/ncomms2387.
Topological insulators are a unique class of materials characterized by a Dirac cone state of helical Dirac fermions in the middle of a bulk gap. When the thickness of a three-dimensional topological insulator is reduced, however, the interaction between opposing surface states opens a gap that removes the helical Dirac cone, converting the material back to a normal system of ordinary fermions. Here we demonstrate, using density function theory calculations and experiments, that it is possible to create helical Dirac fermion state by interfacing two gapped films-a single bilayer Bi grown on a single quintuple layer Bi(2)Se(3) or Bi(2)Te(3). These extrinsic helical Dirac fermions emerge in predominantly Bi bilayer states, which are created by a giant Rashba effect with a coupling constant of ~4 eV·Å due to interfacial charge transfer. Our results suggest that this approach is a promising means to engineer topological insulator states on non-metallic surfaces.
拓扑绝缘体是一类独特的材料，其特征在于在体隙中间存在螺旋狄拉克费米子的狄拉克锥态。然而，当三维拓扑绝缘体的厚度减小时，相反表面态之间的相互作用会打开一个能隙，从而消除螺旋狄拉克锥，使材料恢复为普通费米子的正常系统。在这里，我们使用密度泛函理论计算和实验证明，通过界面两个能隙薄膜——在单个五倍层 Bi(2)Se(3)或 Bi(2)Te(3)上生长的单个双层 Bi——可以创建螺旋狄拉克费米子态。这些外在的螺旋狄拉克费米子主要出现在双层 Bi 态中，这是由于界面电荷转移产生的约 4 eV·Å 的巨大拉什巴效应而产生的。我们的结果表明，这种方法是在非金属表面上设计拓扑绝缘体态的一种很有前途的手段。
