铁硫系超导体中的Tunnel间隙杂质
Tunneling interstitial impurity in iron-chalcogenide based superconductors
摘要：
利用扫描隧道显微镜（STM）研究了$\mathrm{FeTe_{0.5}Se_{0.5}}$超导体中Fe间隙杂质（IFI）及其最近邻位（nn）的带隙内零能束缚态（ZBS）.通过引入一种新的杂质机制，即隧道杂质，并基于Bogoliubove-de Gennes（BDG）方程，我们研究了IFI和底层Fe平面的低能级。我们发现只要IFI和Fe面之间的隧穿参数足够小，并且Fe面深在SC态，ZBS的峰在磁场中不会移动或分裂。我们的结果与实验符合得很好。我们还预测了自旋密度波（SDW）或电荷密度波（CDW）的调制将抑制ZBS的强度。
英文摘要：
A pronounced local in-gap zero-energy bound state (ZBS) has been observed by recent scanning tunneling microscopy (STM) experiments on the interstitial Fe impurity (IFI) and its nearest-neighboring (nn) sites in $\mathrm{FeTe_{0.5}Se_{0.5}}$ superconducting (SC) compound. By introducing a new impurity mechanism, the so-called tunneling impurity, and based on the Bogoliubove-de Gennes (BDG) equations we investigated the low-lying energy states of the IFI and the underlying Fe-plane. We found the peak of ZBS does not shift or split in a magnetic field as long as the tunneling parameter between IFI and the Fe-plane is sufficiently small and the Fe-plane is deep in the SC state. Our results are in good agreement with the experiments. We also predicted that modulation of spin density wave (SDW), or charge density wave (CDW) will suppress the intensity of the ZBS.
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