Department of Physics & Astronomy, University of British Columbia, Vancouver, British Columbia V6T 1Z1, Canada.
Phys Rev Lett. 2013 Nov 22;111(21):216402. doi: 10.1103/PhysRevLett.111.216402. Epub 2013 Nov 19.
By a combined angle-resolved photoemission spectroscopy and density functional theory study, we discover that the surface metallicity is polarity driven in SmB6. Two surface states, not accounted for by the bulk band structure, are reproduced by slab calculations for coexisting B6 and Sm surface terminations. Our analysis reveals that a metallic surface state stems from an unusual property, generic to the (001) termination of all hexaborides: the presence of boron 2p dangling bonds, on a polar surface. The discovery of polarity-driven surface metallicity sheds new light on the 40-year old conundrum of the low-temperature residual conductivity of SmB6, and raises a fundamental question in the field of topological Kondo insulators regarding the interplay between polarity and nontrivial topological properties.
通过角分辨光电子能谱和密度泛函理论的联合研究，我们发现在 SmB6 中表面金属性是由极性驱动的。对于共存的 B6 和 Sm 表面终止，通过薄片计算再现了两个表面态，而这些表面态无法用体能带结构来解释。我们的分析表明，一个金属表面态源于一种不寻常的性质，这种性质对于所有六硼化物的 (001) 终止都是通用的：在极性表面上存在硼 2p 悬空键。极性驱动表面金属性的发现为 SmB6 低温剩余电导率 40 年来的难题提供了新的线索，并在拓扑 Kondo 绝缘体领域提出了一个基本问题，即极性和非平凡拓扑性质之间的相互作用。
