Department of Physics and Astronomy, Interdisciplinary Nanoscience Center, Aarhus University, 8000 Aarhus C, Denmark.
Department of Physics and Shenzhen Institute for Quantum Science and Engineering (SIQSE), Southern University of Science and Technology, Shenzhen 518055, China.
Nano Lett. 2023 Jan 25;23(2):414-421. doi: 10.1021/acs.nanolett.2c03075. Epub 2023 Jan 6.
Heterostructures composed of the intrinsic magnetic topological insulator MnBiTe and its nonmagnetic counterpart BiTe host distinct surface electronic band structures depending on the stacking order and exposed termination. Here, we probe the ultrafast dynamical response of MnBiTe and MnBiTe following near-infrared optical excitation using time- and angle-resolved photoemission spectroscopy and disentangle surface from bulk dynamics based on density functional theory slab calculations of the surface-projected electronic structure. We gain access to the out-of-equilibrium charge carrier populations of both MnBiTe and BiTe surface terminations of MnBiTe, revealing an instantaneous occupation of states associated with the BiTe surface layer followed by carrier extraction into the adjacent MnBiTe layers with a laser fluence-tunable delay of up to 350 fs. The ensuing thermal relaxation processes are driven by phonon scattering with significantly slower relaxation times in the magnetic MnBiTe septuple layers. The observed competition between interlayer charge transfer and intralayer phonon scattering demonstrates a method to control ultrafast charge transfer processes in MnBiTe-based van der Waals compounds.
由本征磁性拓扑绝缘体 MnBiTe 和其非磁性对应物 BiTe 组成的异质结构，根据堆叠顺序和暴露端，具有不同的表面电子能带结构。在这里，我们使用时间和角度分辨光发射谱探测了 MnBiTe 和 MnBiTe 在近红外光激发下的超快动力学响应，并基于 MnBiTe 表面投影电子结构的密度泛函理论薄片计算，从体动力学中解分出表面动力学。我们获得了 MnBiTe 和 MnBiTe 表面终止的非平衡载流子浓度，揭示了与 BiTe 表面层相关的态的瞬时占据，随后载流子被提取到相邻的 MnBiTe 层中，激光强度可调延迟高达 350 fs。随后的热弛豫过程由声子散射驱动，在磁性 MnBiTe 七重层中，弛豫时间明显较慢。观察到的层间电荷转移和层内声子散射之间的竞争表明了一种控制基于 MnBiTe 的范德华化合物中超快电荷转移过程的方法。
