ISSP, University of Tokyo, Kashiwa-no-ha, Kashiwa, Chiba 277-8581, Japan.
1] College of Science, Ibaraki University, Mito, Ibaraki 310-8512, Japan [2] Department of Quantum Matter and Institute for Advanced Materials Research, Hiroshima University, Higashi-hiroshima, Hiroshima 739-8530, Japan.
Sci Rep. 2015 Feb 2;5:8160. doi: 10.1038/srep08160.
Recent studies suggest that an exemplary Kondo insulator SmB6 belongs to a new class of topological insulators (TIs), in which non-trivial spin-polarized metallic states emerge on surface upon the formation of Kondo hybridization gap in the bulk. Remarkably, the bulk resistivity reaches more than 20 Ω cm at 4 K, making SmB6 a candidate for a so-called bulk-insulating TI. We here investigate optical-pulse responses of SmB6 by pump-and-probe photoemission spectroscopy. Surface photovoltage effect is observed below ~90 K. This indicates that an optically-active band bending region develops beneath the novel metallic surface upon the bulk-gap evolution. The photovoltaic effect persists for >200 µs, which is long enough to be detected by electronics devices, and could be utilized for optical gating of the novel metallic surface.
最近的研究表明，典范的 Kondo 绝缘体 SmB6 属于一类新的拓扑绝缘体 (TI)，在这类拓扑绝缘体中，在体相中形成 Kondo 杂化能隙时，表面上会出现非平凡的自旋极化金属态。值得注意的是，SmB6 的体电阻率在 4 K 时超过 20 Ω cm，使其成为所谓的体绝缘 TI 的候选材料。我们在这里通过泵浦和探测光电子能谱研究了 SmB6 的光脉冲响应。在~90 K 以下观察到表面光电压效应。这表明，在体隙演化时，在新的金属表面下会形成一个光活性能带弯曲区域。光生伏特效应持续时间超过 200 μs，足以通过电子设备检测到，并且可用于新金属表面的光学选通。
