论文标题
二维$ s $ - 波超导体的束缚状态聚焦
Quasiparticle focusing of bound states in two-dimensional $s$-wave superconductors
论文作者
论文摘要
超导底物上的磁杂质会引起间隙Yu-Shiba-Rusinov（YSR）结合状态，其复杂的空间结构对工程集体杂质状态的可能性至关重要。通过鞍点的近似，我们研究了散射过程，在间隙，二维超导体中引起YSR状态。此外，我们开发了一种理论，该理论通过简单的分析表达式与二维宿主中正常电子的任意能量分散与YSR状态的空间特征相关。也就是说，我们发现，费米表面的平坦段具有较大的费米速度，从而增强了杂质周围状态（LDOS）的局部密度。我们的分析近似在具有不同费米表面的各种晶格上的紧密结合计算上是定量准确的，并且可以预测在扫描隧道频谱实验中观察到的YSR状态的形状和方向。我们使用$ \ mathrm {nbse} _2 $的模型来说明结果。
A magnetic impurity on a superconducting substrate induces in-gap Yu-Shiba-Rusinov (YSR) bound states, whose intricate spatial structure crucially influences the possibilities of engineering collective impurity states. By means of a saddle-point approximation we study the scattering processes giving rise to YSR states in gapped, two-dimensional superconductors. Further, we develop a theory which relates through a simple analytical expression an arbitrary energy dispersion of normal electrons in a two-dimensional host to the spatial features of the YSR states. Namely, we find that flatter segments of the Fermi surface with large Fermi velocity enhance the local density of states (LDOS) around the impurity. Our analytical approximation is quantitatively accurate against tight-binding calculations on various lattices with different Fermi surfaces, and it allows to predict the shape and orientation of YSR states observed in scanning tunneling spectroscopy experiments. We illustrate our results with a model of $\mathrm{NbSe}_2$.
