Spatial anisotropy of the Kondo screening cloud in a type-II Weyl semimetal
Spatial anisotropy of the Kondo screening cloud in a type-II Weyl semimetal
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II 型韦尔半金属中近藤屏蔽云的空间各向异性
DOI：
10.1103/physrevb.99.235108
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发表时间：
2019
影响因子：
3.7
通讯作者：
Chen Wei Qiang
中科院分区：
文献类型：
--
作者：
Wang Lu Ji;Hu Xing Tai;Li Lin;Xu Dong Hui;Sun Jin Hua;Chen Wei Qiang
本文用变分波函数方法研究了自旋为1/2的磁性杂质在第二类Weyl半金属（WSM）中的近藤屏蔽效应。我们考虑了一类Ⅱ型WSM模型，两个Weyl节点位于$k_z$轴上，Weyl锥的倾斜沿着$k_x$方向.由于电子和空穴的共存，费米能级处的态密度变得有限，导致近藤效应显著增强。因此，磁性杂质和传导电子总是形成束缚态，这种行为不同于I型WSM中的行为，在I型WSM中，束缚态仅在杂化超过临界值时形成。同时，自旋-轨道耦合和费米面的独特几何结构导致了坐标空间中强各向异性的近藤屏蔽云。倾斜项打破了第二类WSM关于$k_z$-轴的旋转对称性，但系统在组合变换$\mathcal{T}R^{y}（\pi）$下保持不变，其中$\mathcal{T}$是时间反演操作，$R^{y}（\pi）$是围绕$y$-轴旋转$\pi$。三个主平面上自旋-自旋关联函数的Laravely修改的对角和非对角分量反映了这种带对称性的变化。最突出的是，倾斜项触发出现非零的非对角分量的自旋自旋相关函数的$x$-$z$主平面。
We theoretically study the Kondo screening of a spin-1/2 magnetic impurity in the bulk of a type-II Weyl semimetal (WSM) by use of the variational wave function method. We consider a type-II WSM model with two Weyl nodes located on the $k_z$-axis, and the tilting of the Weyl cones are along the $k_x$ direction. Due to co-existing electron and hole pockets, the density of states at the Fermi energy becomes finite, leading to a significant enhancement of Kondo effect. Consequently, the magnetic impurity and the conduction electrons always form a bound state, this behavior is distinct from that in the type-I WSMs, where the bound state is only formed when the hybridization exceeds a critical value. Meanwhile, the spin-orbit coupling and unique geometry of the Fermi surface lead to strongly anisotropic Kondo screening cloud in coordinate space. The tilting terms break the rotational symmetry of the type-II WSM about the $k_z$-axis, but the system remains invariant under a combined transformation $\mathcal{T}R^{y}(\pi)$, where $\mathcal{T}$ is the time-reversal operation and $R^{y}(\pi)$ is the rotation about the $y$-axis by $\pi$. Largely modified diagonal and off-diagonal components of the spin-spin correlation function on three principal planes reflect this change in band symmetry. Most saliently, the tilting terms trigger the emergence of non-zero off-diagonal components of spin-spin correlation function on the $x$-$z$ principal plane.