Huong Pham Thi, Nguyen Chuong V, Phuc Huynh V, Hieu Nguyen N, Hoi Bui D, Phuong Le T T
Division of Computational Mathematics and Engineering, Institute for Computational Science, Ton Duc Thang University, Ho Chi Minh City, Vietnam.
Phys Chem Chem Phys. 2020 Jun 7;22(21):12129-12139. doi: 10.1039/d0cp00914h. Epub 2020 May 21.
The fundamental investigation of topological crystalline insulator (TCI) thin films is essential for observing interesting phenomena. In practice, a promising pathway involves the application of electric and magnetic fields to tune the topological phases of TCI thin films. To achieve this, we applied a perpendicular electric field and an in-plane magnetic field to not only tune the Dirac gap of a SnTe(001) thin film and find the phase transition but also to directly connect them with their effects on the group velocity of both massless and massive surface Dirac fermions. The TCI thin film is an inherent insulator due to the hybridization between the front and back surfaces, and it transitions to a semimetal phase at a critical perpendicular electric field due to the Stark effect. Correspondingly, the anisotropic group velocity of the upper (lower) conduction (valence) band decreases (increases) with the electric field at certain momenta. We found that when one of the in-plane Zeeman field components becomes stronger than the intrinsic hybridization potential, the anisotropic Weyl cones with opposite chiralities retrieve at the critical momenta and the corresponding group velocities become zero. Further, the isotropic in-plane Zeeman field leads to rotation of the band structure, as expected, resulting in non-zero group velocities along all directions. Finally, for the sake of completeness, the combined Stark and Zeeman effects are tracked and the results show that the system is an insulator at all fields and the group velocities are altered more than when the individual Stark and Zeeman effects are applied. Our findings may provide interesting physical insights for practical applications in nanoelectronics and spintronics.
对拓扑晶体绝缘体（TCI）薄膜进行基础研究对于观察有趣的现象至关重要。在实际应用中，一条有前景的途径是施加电场和磁场来调控TCI薄膜的拓扑相。为实现这一点，我们施加了一个垂直电场和一个面内磁场，不仅用于调控SnTe(001)薄膜的狄拉克能隙并找到相变点，还将它们与对无质量和有质量表面狄拉克费米子群速度的影响直接联系起来。TCI薄膜由于前后表面之间的杂化作用本质上是绝缘体，并且由于斯塔克效应，在临界垂直电场下会转变为半金属相。相应地，在特定动量下，上（下）导（价）带的各向异性群速度随电场减小（增大）。我们发现，当面内塞曼场分量之一变得比本征杂化势更强时，具有相反手性的各向异性外尔锥在临界动量处恢复，相应的群速度变为零。此外，如预期的那样，面内各向同性塞曼场导致能带结构旋转，从而沿所有方向产生非零群速度。最后，为了完整性，我们追踪了斯塔克效应和塞曼效应的综合影响，结果表明该系统在所有场中都是绝缘体，并且群速度的变化比单独施加斯塔克效应和塞曼效应时更大。我们的发现可能为纳米电子学和自旋电子学的实际应用提供有趣的物理见解。
