Maklar Julian, Stühler Raúl, Dendzik Maciej, Pincelli Tommaso, Dong Shuo, Beaulieu Samuel, Neef Alexander, Li Gang, Wolf Martin, Ernstorfer Ralph, Claessen Ralph, Rettig Laurenz
Fritz-Haber-Institut der Max-Planck-Gesellschaft, Faradayweg 4-6, D-14195 Berlin, Germany.
Physikalisches Institut and Würzburg-Dresden Cluster of Excellence ct.qmat, University of Würzburg, D-97070 Würzburg, Germany.
Nano Lett. 2022 Jul 13;22(13):5420-5426. doi: 10.1021/acs.nanolett.2c01462. Epub 2022 Jun 16.
Two-dimensional quantum spin Hall (QSH) insulators are a promising material class for spintronic applications based on topologically protected spin currents in their edges. Yet, they have not lived up to their technological potential, as experimental realizations are scarce and limited to cryogenic temperatures. These constraints have also severely restricted characterization of their dynamical properties. Here, we report on the electron dynamics of the novel room-temperature QSH candidate bismuthene after photoexcitation using time- and angle-resolved photoemission spectroscopy. We map the transiently occupied conduction band and track the full relaxation pathway of hot photocarriers. Intriguingly, we observe photocarrier lifetimes much shorter than those in conventional semiconductors. This is ascribed to the presence of topological in-gap states already established by local probes. Indeed, we find spectral signatures consistent with these earlier findings. Demonstration of the large band gap and the view into photoelectron dynamics mark a critical step toward optical control of QSH functionalities.
二维量子自旋霍尔（QSH）绝缘体是一类很有前景的材料，适用于基于其边缘拓扑保护自旋电流的自旋电子学应用。然而，它们尚未发挥出其技术潜力，因为实验实现很少，且仅限于低温温度。这些限制也严重制约了对其动力学性质的表征。在此，我们使用时间和角度分辨光电子能谱报告了新型室温QSH候选材料铋烯在光激发后的电子动力学。我们绘制了瞬态占据的导带，并追踪了热光载流子的完整弛豫路径。有趣的是，我们观察到光载流子寿命比传统半导体中的要短得多。这归因于局部探针已经建立的拓扑带隙态的存在。事实上，我们发现了与这些早期发现一致的光谱特征。大带隙的证明以及对光电子动力学的洞察标志着朝着QSH功能的光学控制迈出了关键一步。
