Topological insulators (TIs) with unique band structures have wide application prospects in the fields of ultrafast optical and spintronic devices. The dynamics of hot carriers plays a key role in these TI-based devices. In this work, using the time- and angle-resolved photoemission spectroscopy technique, the relaxation process of the hot carriers in Cr-doped Bi₂Se₃ has been systematically studied since the ferromagnetic TI is one of the key building blocks for next-generation spintronics. It is found that electronic temperature (T_e) and chemical potential (μ) decrease faster with the increase in the Cr doping concentration. Similarly, the lifetime (τ) of the excited electrons also decreases with more Cr doped into Bi₂Se₃. The results suggest a mechanism of impurity band-assisted carrier relaxation, where the impurity band within the bulk bandgap introduced by Cr doping provides significant recombination channels for the excited electrons. This work directly illustrates the dynamic process of the photon-generated carriers in Cr-doped Bi₂Se₃, which is expected to promote the applications of (Bi_1-xCr_x)₂Se₃ in photoelectric devices.

中文翻译：

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Cr掺杂拓扑绝缘子Bi2Se3中的杂质带辅助载流子弛豫

具有独特带结构的拓扑绝缘体（TI）在超快光学和自旋电子器件领域具有广阔的应用前景。热载流子的动态特性在这些基于TI的设备中起着关键作用。在这项工作中，使用时间分辨和角度分辨光发射光谱技术，由于铁磁TI是下一代的关键构建模块之一，因此系统地研究了Cr掺杂Bi ₂ Se _3中热载流子的弛豫过程。自旋电子学。发现随着Cr掺杂浓度的增加，电子温度（T _e）和化学势（μ）下降得更快。同样，寿命（τ随着更多的Cr掺杂到Bi ₂ Se ₃中，激发电子的）也减小。结果提示了杂质带辅助载流子弛豫的机理，其中通过Cr掺杂引入的体带隙内的杂质带为激发的电子提供了重要的复合通道。这项工作直接说明了Cr掺杂的Bi ₂ Se _3中光子产生载流子的动态过程，有望促进（Bi _1-x Cr _x）₂ Se ₃在光电器件中的应用。