电子掺杂 FeSe 单层中伴随 Lifshitz 转变的增强超导电性。
Enhanced superconductivity accompanying a Lifshitz transition in electron-doped FeSe monolayer.
机构信息
Beijing National Laboratory for Condensed Matter Physics and Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China.
Department of Physics, Beijing Key Laboratory of Opto-Electronic Functional Materials and Micro-nano Devices, Renmin University of China, Beijing 100872, China.
出版信息
Nat Commun. 2017 Apr 19;8:14988. doi: 10.1038/ncomms14988.
The origin of enhanced superconductivity over 50 K in the recently discovered FeSe monolayer films grown on SrTiO (STO), as compared to 8 K in bulk FeSe, is intensely debated. As with the ferrochalcogenides AFeSe and potassium-doped FeSe, which also have a relatively high-superconducting critical temperature (T), the Fermi surface (FS) of the FeSe/STO monolayer films is free of hole-like FS, suggesting that a Lifshitz transition by which these hole FSs vanish may help increasing T. However, the fundamental reasons explaining this increase of T remain unclear. Here we report a 15 K jump of T accompanying a second Lifshitz transition characterized by the emergence of an electron pocket at the Brillouin zone centre, which is triggered by high-electron doping following in situ deposition of potassium on FeSe/STO monolayer films. Our results suggest that the pairing interactions are orbital dependent in generating enhanced superconductivity in FeSe.
在 SrTiO（STO）上生长的 FeSe 单层膜中发现的超导增强现象，其超导转变温度超过 50K，相比之下，体相 FeSe 的超导转变温度仅为 8K。与具有相对较高超导转变温度（T）的铁硫族化合物 AFeSe 和钾掺杂的 FeSe 类似，FeSe/STO 单层膜的费米面（FS）中没有空穴型 FS，这表明费米面的 Lifshitz 转变可能有助于提高 T。然而，解释 T 增加的基本原因仍不清楚。在这里，我们报告了 T 的 15K 跃变，这伴随着第二个 Lifshitz 转变，其特征是布里渊区中心出现电子口袋，这是通过在原位沉积钾后对 FeSe/STO 单层膜进行高电子掺杂而触发的。我们的结果表明，在 FeSe 中，配对相互作用与轨道有关，这导致了超导增强。
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