AI 中文总结
研究探讨在无隙物质中实现量子霍尔效应这一挑战，利用手性拓扑半金属Rh0.95Ni0.05Si，通过镍取代打开光子能量窗口，观察到量子化圆光电流效应，建立了量子霍尔效应全光模拟及无隙物质拓扑量子化新范式。
AI 中文摘要
有隙系统中的量子霍尔效应代表了非平凡拓扑的一个决定性特征。在无隙物质中实现这一原理一直是量子材料领域的核心挑战。手性拓扑半金属提供了一个独特的平台，可通过作为贝里曲率单极子的对称性保护多折交叉来实现这一目标。当光学跃迁局限于单个多折节点时，预计产生的圆光电流效应会根据节点的拓扑电荷进行量子化。然而在实际材料中，这一现象在实验上仍然难以捉摸，受到平凡带跃迁、节点对之间的能量分离以及它们相对于费米能级的相对位置的影响。本文中，我们在手性拓扑半金属Rh0.95Ni0.05Si中观察到了量子化的圆光电流效应。镍取代在Γ点多折节点处打开了一个由带间光学跃迁主导的光子能量窗口。这使得圆偏振近红外到中红外脉冲能够驱动一种螺旋度奇数的太赫兹响应，该响应表现出量子化的三个特征：急剧起始、由单极电荷大小决定的与波长无关 的平台以及由泡利阻塞引起的突然截止。我们的工作建立了量子霍尔效应的全光模拟以及无隙物质中拓扑量子化的新范式。
英文摘要
The quantum Hall effect establishes that topology can fix a material response to integer multiples of fundamental constants when an energy gap isolates the relevant symmetry-protected electronic states. Whether such universal quantization can also emerge in gapless matter, where topological bands coexist with a continuum of metallic excitations, has remained a fundamental question in the field of quantum materials. Chiral topological semimetals provide a unique setting in which to explore this principle; when optical transitions are confined to a single chiral node, the resulting circular photogalvanic effect is predicted to be quantized by the topological charge of the node. In real materials, however, this nonlinear optical phenomenon has remained experimentally elusive, obscured by trivial band transitions, insufficient energy separation between node pairs, and their relative positions with respect to the Fermi level. Here we observe a quantized circular photogalvanic effect in the chiral topological semimetal Rh0.95Ni0.05Si. Band engineering via Ni substitution opens a photon-energy window dominated by interband optical transitions at the Γ-point multifold node. This allows circularly polarized near- to mid-infrared pulses to drive a helicity-odd terahertz response that manifests three hallmarks of quantization: a sharp onset, a photon-energy-independent plateau governed by the magnitude of the monopole charge, and an abrupt long-wavelength cutoff imposed by Pauli blocking. Our work thus establishes an all-optical analogue of the quantum Hall effect and a new paradigm to realize topological quantization in gapless matter.
