Sumida K, Ishida Y, Zhu S, Ye M, Pertsova A, Triola C, Kokh K A, Tereshchenko O E, Balatsky A V, Shin S, Kimura A
Graduate School of Science, Hiroshima University, 1-3-1 Kagamiyama, Higashi-Hiroshima, Hiroshima 739-8526, Japan.
ISSP, University of Tokyo, 5-1-5, Kashiwa-no-ha, Chiba 277-8581, Japan.
Sci Rep. 2017 Oct 26;7(1):14080. doi: 10.1038/s41598-017-14308-w.
Topological insulators (TIs) possess spin-polarized Dirac fermions on their surface but their unique properties are often masked by residual carriers in the bulk. Recently, (Sb Bi )Te was introduced as a non-metallic TI whose carrier type can be tuned from n to p across the charge neutrality point. By using time- and angle-resolved photoemission spectroscopy, we investigate the ultrafast carrier dynamics in the series of (Sb Bi )Te. The Dirac electronic recovery of ∼10 ps at most in the bulk-metallic regime elongated to >400 ps when the charge neutrality point was approached. The prolonged nonequilibration is attributed to the closeness of the Fermi level to the Dirac point and to the high insulation of the bulk. We also discuss the feasibility of observing excitonic instability of (Sb Bi )Te.
拓扑绝缘体（TIs）在其表面拥有自旋极化的狄拉克费米子，但其独特性质常常被体内的残余载流子所掩盖。最近，（SbBi）Te被引入作为一种非金属拓扑绝缘体，其载流子类型可以在电荷中性点处从n型调谐到p型。通过使用时间分辨和角分辨光电子能谱，我们研究了（SbBi）Te系列中的超快载流子动力学。在体金属区域中，狄拉克电子的恢复时间最长约为10皮秒，而当接近电荷中性点时，该时间延长至>400皮秒。这种延长的非平衡状态归因于费米能级与狄拉克点的接近以及体材料的高绝缘性。我们还讨论了观察（SbBi）Te激子不稳定性的可行性。
