Electron states scattering off line edges on the surface of topological insulator

• Published in: Chinese physics B Vol. 23; no. 10; pp. 477 - 482
• Main Author: 邵怀华 刘一曼 周小英 周光辉
• Format: Journal Article
• Language: English
• Published: 01.10.2014
• Subjects: Constants; Decay; Defects; Insulators; Oscillations; Refraction; Scattering; Three dimensional; Topology; 体表面; 局域态密度; 拓扑; 状态; 电子散射; 离线; 绝缘体; 衰减行为
• ISSN: 1674-1056; 2058-3834; 1741-4199
• DOI: 10.1088/1674-1056/23/10/107304

We study the local density of states （LDOS） for electrons scattering off the line edge of an atomic step defect on the surface of a three-dimensional （3D） topological insulator （TI） and the line edge of a finite 3D TI, where the front surface and side surface meet with different Fermi velocities, respectively. By using a S-function potential to model the edges, we find that the bound states existed along the step line edge significantly contribute to the LDOS near the edge, but do not modify the exponential behavior away from it. In addition, the power-law decaying behavior for LDOS oscillation away from the step is understood from the spin rotation for surface states scattering off the step defect with magnitude depending on the strength of the potential. Furthermore, the electron refraction and total reflection analogous to optics occurred at the line edge where two surfaces meet with different Fermi velocities, which leads to the LDOS decaying behavior in the greater Fermi velocity side similar to that for a step line edge. However, in the smaller velocity side the LDOS shows a different decaying behavior as x-1/2, and the wavevector of LDOS oscillation is no longer equal to the diameter of the constant energy contour of surface band, but is sensitively dependent on the ratio of the two Fermi velocities. These effects may be verified by STM measurement with high precision.