Liu Qiya, Zhang Min, Yang Xinsheng, Zeng Tixian, Pan Minghu
College of Optoelectronic Technology, Chengdu University of Information Technology, Chengdu 610225, China.
Superconductivity and New Energy R&D Center, School of Physical Science and Technology, Southwest Jiaotong University, Chengdu 610031, China.
Nanomaterials (Basel). 2025 Jun 30;15(13):1010. doi: 10.3390/nano15131010.
Topological insulators (TIs) can be widely applied in the fields of ultrafast optical and spintronic devices owing to the existence of topologically protected gapless Dirac surface states. However, the study of ultrafast dynamics of carriers in TIs remains elusive. In this work, the carrier dynamics of Li-doped BiSe single crystals were investigated by femtosecond (fs) transient optical spectroscopy (ΔR/R(t) signals). The temperature dependence for the relaxation rates of the electron-electron interaction and electron-phonon coupling is consistent with the results of electrical transport, which indicates the carrier dynamics of TI is highly related with carrier concentrations. We find that the carrier type and concentration of BiSe can be tuned by Li doping, leading to a metal-insulation transition at low temperatures (T ≤ 55 K), indicating that electron-electron interactions are dominant at low temperature. For T > 55 K, electron-phonon coupling in the bulk carriers becomes the main electric transport mechanism.
由于存在拓扑保护的无隙狄拉克表面态，拓扑绝缘体（TIs）可广泛应用于超快光学和自旋电子器件领域。然而，对拓扑绝缘体中载流子超快动力学的研究仍然难以捉摸。在这项工作中，通过飞秒（fs）瞬态光谱（ΔR/R(t)信号）研究了锂掺杂BiSe单晶的载流子动力学。电子 - 电子相互作用和电子 - 声子耦合弛豫率的温度依赖性与电输运结果一致，这表明拓扑绝缘体的载流子动力学与载流子浓度高度相关。我们发现，BiSe的载流子类型和浓度可以通过锂掺杂来调节，从而在低温（T≤55 K）下导致金属 - 绝缘转变，这表明电子 - 电子相互作用在低温下占主导地位。对于T>55 K，体载流子中的电子 - 声子耦合成为主要的电输运机制。
