Possible structural origin of superconductivity in Sr-doped Bi2Se3
Possible structural origin of superconductivity in Sr-doped Bi2Se3
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Sr 掺杂 Bi2Se3 超导性的可能结构起源
DOI：
10.1103/physrevmaterials.2.014201
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发表时间：
2018
影响因子：
3.4
通讯作者：
Gao Bo
中科院分区：
文献类型：
--
作者：
Li Zhuojun;Wang Meng;Zhang Dejiong;Feng Nan;Jiang Wenxiang;Han Chaoqun;Chen Weijiong;Ye Mao;Gao Chunlei;Jia Jinfeng;Li Jixue;Qiao Shan;Qian Dong;Xu Ben;Tian He;Gao Bo
在硒化铋中掺杂铜和锶等元素可以诱导超导性，使掺杂材料成为探索潜在拓扑超导行为的有趣候选者。认为掺杂的超导电性是由掺杂原子嵌入货车德瓦耳斯能隙引起的。然而，一些实验表明，掺杂剂原子的嵌入并不一定使掺杂超导。因此，掺杂的超导性的结构起源仍然是一个悬而未决的问题。在此，我们结合材料合成与表征、高分辨透射电子显微镜和第一性原理计算来研究Sr掺杂的掺杂结构。我们发现，超导电性的出现与型掺杂原子密切相关。原子水平的能量色散X射线映射揭示了各种类型的Sr掺杂剂，占据插层和间隙的位置。第一性原理计算表明，一个特定的间隙Sr掺杂位置的形成能强烈依赖于Sr掺杂水平。该位置从低Sr掺杂水平下的亚稳位置变化到高Sr掺杂水平下的稳定位置。计算结果解释了为什么淬火是必要的，以获得超导样品时，Sr掺杂水平低，也为什么慢炉冷却时，Sr掺杂水平高，可以产生超导样品。我们的研究结果表明，Sr原子掺杂在间隙的位置，而不是那些插入在货车德瓦耳斯间隙，是最有可能负责的超导性的出现在Sr掺杂。
Doping bismuth selenide () with elements such as copper and strontium (Sr) can induce superconductivity, making the doped materials interesting candidates to explore potential topological superconducting behaviors. It was thought that the superconductivity of dopedwas induced by dopant atoms intercalated in van der Waals gaps. However, several experiments have shown that the intercalation of dopant atoms may not necessarily make dopedsuperconducting. Thus, the structural origin of superconductivity in dopedremains an open question. Herein, we combined material synthesis and characterization, high-resolution transmission electron microscopy, and first-principles calculations to study the doping structure of Sr-doped. We found that the emergence of superconductivity is strongly related with-type dopant atoms. Atomic-level energy-dispersive x-ray mapping revealed various-type Sr dopants that occupy intercalated and interstitial positions. First-principles calculations showed that the formation energy of a specific interstitial Sr doping position depends strongly on the Sr doping level. This site changes from a metastable position at low Sr doping level to a stable position at high Sr doping level. The calculation results explain why quenching is necessary to obtain superconducting samples when the Sr doping level is low and also why slow furnace cooling can yield superconducting samples when the Sr doping level is high. Our findings suggest that Sr atoms doped at interstitial locations, instead of those intercalated in van der Waals gaps, are most likely to be responsible for the emergence of superconductivity in Sr-doped.