Weak topological insulators (TIs) host non-trivial topological surface state bands (SSBs) at the side surface of the crystal while the top (001) surface can be topologically either dark or light. In our detailed angle-resolved photoelectron spectroscopy (ARPES) study we found Dirac-like linearly dispersive SSBs on the (001) surface of BiSe and Sb-doped (8%) BiSe. The lower part of the SSBs buries deep in the bulk valence band (BVB) and the overlap region between the SSBs and BVB increases significantly with Sb doping. These results highlight the role of the interlayer coupling between the Bi bilayer and the Bi₂Se₃ quintuple layer (QL). Furthermore, in the overlap region the SSBs deviate from the Dirac-like linear dispersion. Interestingly, we observed a large intensity imbalance ) in the SSBs located at the positive and negative directions. This asymmetry pattern ) gradually reverses to ) as the excitation energy scans from low (14 eV) to high (34 eV) values. The observed photon energy-dependent intensity variation could be a signature of the mixing between the spin and the orbit texture of the SSBs.

弱拓扑绝缘体 (TI) 在晶体的侧表面拥有非平凡的拓扑表面态带 (SSB)，而顶部 (001) 表面在拓扑上可以是暗的或亮的。在我们详细的角分辨光电子能谱 (ARPES) 研究中，我们在 BiSe 和 Sb 掺杂 (8%) BiSe 的 (001) 表面上发现了类似狄拉克的线性色散 SSB。SSB 的下部深埋在体价带 (BVB) 中，SSB 和 BVB 之间的重叠区域随着 Sb 掺杂显着增加。这些结果突出了 Bi 双层和 Bi ₂ Se ₃五重层 (QL)之间层间耦合的作用。此外，在重叠区域中，SSB 偏离了类狄拉克线性色散。有趣的是，我们观察到了很大的强度不平衡) 在位于正方向和负方向的 SSB 中。当激发能量从低 (14 eV) 扫描到高 (34 eV) 值时，这种不对称模式) 逐渐反转为)。观察到的光子能量依赖强度变化可能是 SSB 的自旋和轨道纹理之间混合的标志。