AI 中文总结
研究在室温下于Rashba型极性半导体BiTeCl中观测到80倍于此前最佳表面主导体系的巨大表面驱动二阶非线性霍尔效应，揭示极性晶体相对表面不对称性为相关材料设计通用原则。
AI 中文摘要
非线性霍尔效应（NLHE）为时间反演对称但破缺中心反演对称的体系提供了产生霍尔响应的途径。NLHE可将交流电整流为横向直流电压，使其在射频整流、能量收集和太赫兹探测等应用中极具吸引力，而器件小型化仍是这些应用的核心追求。在此背景下，表面固有的中心反演对称破缺尤为引人关注：因为任何晶体表面的对称性必然破缺，无论其体相是否为中心对称，表面驱动的非线性响应突破了对体相对称性的严格限制，为紧凑器件架构开辟了路径。本文中，我们报道了在Rashba型极性半导体BiTeCl中室温下观测到的巨大的、表面驱动的二阶非线性霍尔效应。300 K下测得的二阶非线性霍尔极化率达到1.68 μmV⁻¹，是此前报道的最佳表面主导体系的80倍。我们将这一巨大响应归因于BiTeCl的极性晶体结构与其丰富的表面态的协同相互作用：极性堆叠使顶表面和底表面不等价，因此非线性响应源自单一表面，无另一表面的补偿。对称性分析和标度分析表明，斜散射和侧跳机制均对观测到的效应有贡献。我们的发现不仅确定BiTeCl是未来利用NLHE的应用的有前景的平台，还确立了极性晶体相对表面之间的不对称性作为发现具有更大非线性霍尔响应的表面驱动材料的通用设计原则。
英文摘要
The nonlinear Hall effect (NLHE) provides a pathway to generate a Hall response in time-reversal-symmetric yet inversion-symmetry-broken systems. NLHE can rectify an alternating current into a transverse direct voltage, making it attractive for radio-frequency rectification, energy harvesting, and terahertz detection, applications for which device miniaturization remains a central pursuit. In this context, the inherent inversion symmetry breaking at surfaces is particularly appealing: because symmetry is necessarily broken at the surface of any crystal, irrespective of whether its bulk is centrosymmetric, surface-driven nonlinear responses lift the stringent constraint on bulk symmetry and open a route toward compact device architectures. Here we report the observation of a giant, surface-driven second-order nonlinear Hall effect in the Rashba-type polar semiconductor BiTeCl at room temperature. The determined second-order nonlinear Hall susceptibility at 300 K reaches 1.68 $μ$mV$^{-1}$, which is 80 times larger than that of the best previously reported surface-dominated systems. We attribute this giant response to the synergistic interplay between BiTeCl's polar crystal structure and its rich surface states: the polar stacking renders the top and bottom surfaces inequivalent, so that the nonlinear response originates from a single surface without compensation from the other. Symmetry and scaling analyses suggest that both skew-scattering and side-jump mechanisms contribute to the observed effect. Our findings not only identify BiTeCl as a promising platform for future applications utilizing the NLHE, but also establish the asymmetry between the opposite surfaces of a polar crystal as a general design principle for discovering surface-driven materials with larger nonlinear Hall responses.
