Nanosecond dynamics in intrinsic topological insulator Bi2−xSbxSe3 revealed by time-resolved optical reflectivity
Nanosecond dynamics in intrinsic topological insulator Bi2−xSbxSe3 revealed by time-resolved optical reflectivity
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DOI：
10.1103/physrevb.103.l020301
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发表时间：
2021-01
影响因子：
3.7
通讯作者：
Adam L. Gross;Yasen Hou;A. Rossi;Dong Yu;I. Vishik
中科院分区：
文献类型：
--
作者：
Adam L. Gross;Yasen Hou;A. Rossi;Dong Yu;I. Vishik
${\mathrm{Bi}}_{2}{\mathrm{Se}}_{3}$是一种理想的三维拓扑绝缘体，其中化学势可以通过锑掺杂带入体带隙。在这里，我们利用超快时间分辨瞬态反射率来表征 ${\mathrm{Bi}}_{2\ensuremath{-}x}{\mathrm{Sb}}_{x}{\mathrm{Se}}_{3}$ 纳米片中的光激发载流子衰变。我们报告称，与$n$型散装金属${\mathrm{Bi}}_{2}{\mathrm{Se}}_{3}$相比，低温下散装绝缘${\mathrm{Bi}}_{2\ensuremath{-}x}{\mathrm{Sb}}_{x}{\mathrm{Se}}_{3}$的散装载体弛豫时间显着减慢，接近$3.3\phantom{\rule{0.16em}{0ex}}\mathrm{ns}$ 在零泵注量限制中。这种长期衰变与不同注量和锑浓度相关，揭示了 $n$ 型 ${\mathrm{Bi}}_{2}{\mathrm{Se}}_{3}$ 中不存在的独特衰变动力学，即散装载体的缓慢双分子重组。
${\mathrm{Bi}}_{2}{\mathrm{Se}}_{3}$ is an ideal three-dimensional topological insulator in which the chemical potential can be brought into the bulk band gap with antimony doping. Here, we utilize ultrafast time-resolved transient reflectivity to characterize the photoexcited carrier decay in ${\mathrm{Bi}}_{2\ensuremath{-}x}{\mathrm{Sb}}_{x}{\mathrm{Se}}_{3}$ nanoplatelets. We report a substantial slowing of the bulk carrier relaxation time in bulk-insulating ${\mathrm{Bi}}_{2\ensuremath{-}x}{\mathrm{Sb}}_{x}{\mathrm{Se}}_{3}$ as compared to $n$-type bulk-metallic ${\mathrm{Bi}}_{2}{\mathrm{Se}}_{3}$ at low temperatures, which approaches $3.3\phantom{\rule{0.16em}{0ex}}\mathrm{ns}$ in the zero pump fluence limit. This long-lived decay is correlated across different fluences and antimony concentrations, revealing unique decay dynamics not present in $n$-type ${\mathrm{Bi}}_{2}{\mathrm{Se}}_{3}$, namely the slow bimolecular recombination of bulk carriers.