ARPES measurements of the topological insulator, Bi2Se3, and Ga/Cu-doped Bi2Se3

Topological insulators (TIs) possess surface states and high mobility, due to the presence of strong spin-orbit coupling and time-reversal symmetry (TRS). Bi2Se3 is one of the most promising TI due to its relatively large bandgap (0.3 eV), making it the most suitable to work at room temperature. The bulk of Bi2Se3 tends to become n-type degenerate moving the chemical potential toward the conduction band. Though by doping, it is possible to move the chemical potential into the bandgap within the surface states. We use a molecular beam epitaxy (MBE) to grow high-quality single-crystal thin films of Bi2Se3 and gallium and copper-doped Bi2Se3. The addition of gallium and copper leads to an expansion of the crystal lattice and the formation of extra conductive channels. There is a possibility of topological superconductivity (TS) by doping with Ga and Cu. By performing ARPES measurements, we will be able to obtain detailed electronic band structure, providing fundamental knowledge of the doping influence at the surface states and the Fermi Surface of the topological insulator.

拓扑绝缘体（Topological Insulators, TIs）因强自旋轨道耦合与时间反演对称性（Time-Reversal Symmetry, TRS）的存在，具备表面态与高迁移率特性。硒化铋（Bi₂Se₃）因拥有相对较大的带隙（0.3 eV），是最具应用潜力的拓扑绝缘体之一，也是最适合在室温下工作的拓扑绝缘体材料。硒化铋本体往往会呈现n型简并状态，导致化学势向导带方向偏移。不过通过掺杂手段，可将化学势调控至表面态所在的带隙区间内。我们采用分子束外延（Molecular Beam Epitaxy, MBE）制备了高质量的硒化铋、镓掺杂硒化铋与铜掺杂硒化铋单晶薄膜。镓与铜的掺入会引发晶格膨胀，并形成额外的导电通道。通过镓、铜掺杂有望实现拓扑超导性（Topological Superconductivity, TS）。借助角分辨光电子能谱（ARPES）测量，可获取详尽的电子能带结构信息，从而为理解掺杂对拓扑绝缘体表面态及费米面（Fermi Surface）的影响提供基础认知。