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Impurity band assisted carrier relaxation in Cr doped topological insulator Bi2Se3

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  • Jian Tu
  • Yafei Zhao
  • Xiaoqian Zhang
  • Zhonghui Nie
  • Yao Li
  • Yilin Zhang
  • Ion Cristian Edmond Turcu
  • Luca Poletto
  • Fabio Frassetto
  • Xuezhong Ruan
  • Wenbin Zhong
  • Xuefeng Wang
  • Wenqing Liu
  • Yu Zhang
  • Rong Zhang
  • Yongbing Xu
  • Liang He


Publication details

JournalApplied Physics Letters
DatePublished - 23 Feb 2021
Issue number8
Original languageEnglish


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 (Te) 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 (Bi1-xCrx)2Se3 in photoelectric devices.

Bibliographical note

Funding Information:
This work was supported by the National Key Research and Development Program of China (No. 2016YFA0300803), the National Natural Science Foundation of China (Nos. 61974061, 61674079, 61427812, and 61805116), the Natural Science Foundation of Jiangsu Province of China (Nos. BK20192006 and BK20180056), and the China Postdoctoral Science Foundation (No. 2019M661787).

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