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标题：Emergent photovoltage on SmB₆ surface upon bulk-gap evolution revealed by pump-and-probe photoemission spectroscopy
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作者：Y. Ishida ; T. Otsu ; T. Shimada 等
期刊名称：Scientific Reports
电子版ISSN：2045-2322
出版年度：2015
卷号：5
DOI：10.1038/srep08160
出版社：Springer Nature
摘要：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 µ s, which is long enough to be detected by electronics devices, and could be utilized for optical gating of the novel metallic surface.