Chirality, a pervasive phenomenon in nature, is widely studied across diverse fields including the origins of life, chemical catalysis, drug discovery, and physical optoelectronics. The investigations of natural chiral materials have been constrained by their intrinsically weak chiral effects. Recently, significant progress has been made in the fabrication and assembly of low-dimensional micro and nanoscale chiral materials and their architectures, leading to the discovery of novel optoelectronic phenomena such as circularly polarized light emission, spin and charge flip, advocating great potential for applications in quantum information, quantum computing, and biosensing. Despite these advancements, the fundamental mechanisms underlying the generation, propagation, and amplification of chirality in low-dimensional chiral materials and architectures remain largely unexplored. To tackle these challenges, we focus on employing ultrafast spectroscopy to investigate the dynamics of chirality evolution, with the aim of attaining a more profound understanding of the microscopic mechanisms governing chirality generation and amplification. This review thus provides a comprehensive overview of the chiral micro-/nano-materials, including two-dimensional transition metal dichalcogenides (TMDs), chiral halide perovskites, and chiral metasurfaces, with a particular emphasis on the physical mechanism. This review further explores the advancements made by ultrafast chiral spectroscopy research, thereby paving the way for innovative devices in chiral photonics and optoelectronics.
Ultrafast helicity control of surface currents in topological insulators with near-unity fidelity
近年来，出现了一类称为三维拓扑绝缘体的固态材料。在本体中，拓扑绝缘体的行为与带隙的普通绝缘体一样。在表面，存在导电的无带隙状态，显示出显著的性质，如螺旋狄拉克色散和抑制自旋极化的载流子的背散射。通过传输实验表征和控制表面状态往往受到阻碍，但在低温下的剩余散装贡献。在这里，我们表明，在Bi 2 Se 3的表面电流可以控制圆偏振光在皮秒的时间尺度上的保真度接近统一，即使在室温下。我们揭示了这种超快的螺旋度依赖的表面电流的时间分离的光致热电和漂移电流的散装。我们的研究结果揭示了基于拓扑绝缘体表面电流的超快光电子器件的功能。
Helicity-Resolved Spatiotemporal Mapping of Chiral Plexcitons in Helicoids
Seoul National University（首尔大学）；Lund University（隆德大学）；United Arab Emirates University（阿联酋大学）；Korea Research Institute of Standards and Science (KRISS)（韩国标准科学研究院）
Ultrafast manipulation of magnetic skyrmions by microwave fields
School of Materials and Physics, China University of Mining and Technology（中国矿业大学材料科学与工程学院）；Center for Quantum Matter, School of Physics, Zhejiang University（浙江大学物理学院量子物质研究中心）
Ultrafast dynamics of photocurrents in surface states of 3D topological insulators
本文综述了利用时间分辨和角度分辨双光子光电子能谱（2PPE）对三维拓扑绝缘体拓扑表面态（TSS）中超快电子动力学的实验研究。重点放在超快光电流的产生及其衰变的时间分辨观察。2PPE不仅允许明确地将光电流与自旋极化电子表面态相关联。探测携带电流的电子的不对称动量分布，使得有可能在时域中研究支配不寻常的电子输运的微观散射过程。超短中红外泵浦脉冲不仅可以直接激发Sb $_2$ Te $_3$中的TSS，而且还可以导致TSS粒子数在动量空间中的强不对称性。TSS的二维能带映射表明，这种不对称性实际上是代表一个宏观的光电流，而螺旋度依赖的光电流被发现是小的。光电流衰减的时间分辨观测揭示了TSS中电子的巨大平均自由程。
