Weyl半金属CoSi中表面电荷密度波的二次谐波产生光谱研究
Second Harmonic Generation Spectroscopy of the Surface Charge Density Wave in the Weyl Semimetal CoSi
浏览论文内容
中文总结 AI 辅助
通过RA-SHG技术发现Weyl半金属CoSi表面存在纯表面驱动的CDW相变，临界指数符合3D XY普适类，归因于表面费米弧态与体拓扑的耦合。
中文摘要 AI 辅助
采用温度依赖的旋转各向异性二次谐波产生（RA-SHG）技术，我们在CoSi（001）表面识别出电荷密度波（CDW）不稳定性，其转变起始温度为90.0±0.8 K。SHG响应追踪序参量振幅，由两个非线性张量元素主导，扣除背景后的强度随温度呈幂律演化，提取的临界指数β=0.30±0.03，与3D XY普适类一致，这对于名义上的二维表面层而言是意外结果。体响应中未观测到对应异常，表明该转变为纯表面驱动的相变。我们将这种意外标度归因于表面费米弧态与其关联的体拓扑之间的耦合，该耦合基于先前观测到的表面亚层间的晶胞内相位关系，该关系赋予序参量本征三维结构。
英文摘要
Using temperature-dependent rotational anisotropy second harmonic generation (RA-SHG), we identify a charge density wave (CDW) instability on the CoSi (001) face with an onset temperature at $90.0 \pm 0.8$ K. The SHG response tracks the order parameter amplitude, dominated by two nonlinear tensor elements, whose background-subtracted intensity evolves with temperature as a power law. The extracted critical exponent $β= 0.30 \pm 0.03$ is consistent with the 3D XY universality class, an unexpected result for a nominally two-dimensional surface layer. No corresponding anomaly is observed in the bulk response, establishing the transition as a purely surface-driven phase transition. We attribute this unexpected scaling to the coupling between surface Fermi-arc states and the bulk topology they are tied to, grounded in a previously observed intra-unit-cell phase relationship between surface sublayers that gives the order parameter intrinsic three-dimensional structure.
