Pooyan Siamak, Hosseini Mir Vahid
Department of Physics, Faculty of Science, University of Zanjan, Zanjan, 45371-38791, Iran.
Sci Rep. 2022 Sep 13;12(1):15379. doi: 10.1038/s41598-022-19756-7.
We consider a disordered topological insulator thin film placed on the top of a ferromagnetic insulator with a perpendicular exchange field M and subjected to a perpendicular electric field. The presence of ferromagnetic insulator causes that bottom surface states of the topological insulator thin film become spin polarized and the electric field provides a potential difference V between the two surface states, resulting in breaking of time-reversal and inversion symmetry in the system. Using Kubo formalism and employing the first Born approximation as well as the self-consistent Born approximation, we calculate the spin Hall conductivity. We find that for small values of V, a large spin conductivity can be generated through large values of M away from the charge neutrality point. But for large values of V, the spin conductivity can be promoted even with small values of M around the charge neutrality point. The effect of vertex corrections and the stability of the obtained large spin conductivity against disorders are also examined.
我们考虑一个无序拓扑绝缘体薄膜，它放置在具有垂直交换场(M)的铁磁绝缘体顶部，并受到垂直电场作用。铁磁绝缘体的存在使得拓扑绝缘体薄膜的底面态发生自旋极化，而电场在两个表面态之间提供了电势差(V)，导致系统中的时间反演对称性和空间反演对称性被打破。我们使用久保形式理论，并采用一级玻恩近似以及自洽玻恩近似来计算自旋霍尔电导率。我们发现，对于较小的(V)值，远离电荷中性点时通过较大的(M)值可以产生较大的自旋电导率。但对于较大的(V)值，即使在电荷中性点附近(M)值较小时，自旋电导率也可以得到提升。我们还研究了顶点修正的影响以及所获得的大自旋电导率对无序的稳定性。
