# Surface Second Harmonic Generation from Topological Dirac Semimetal PdTe$\_2$ Source: [Surface Second Harmonic Generation from Topological Dirac Semimetal PdTe$\_2$]() Collection index: [llms.txt]() Data updated: 2025-10-25T06:38:38.120Z Authors: Syed Mohammed Faizanuddin, Ching-Hang Chien, Yao-Jui Chan, Si-Tong Liu, Chia-Nung Kuo, Chin Shuan Lue, Yu-Chieh Wen Published: 2023-08-17T15:38:56.000Z ## Abstract Recent experiments and calculations in topological semimetals have observed anomalously strong second-order optical nonlinearity, but yet whether the enhancement also occurs at surfaces of topological semimetals in general remains an open question. In this work, we tackle this problem by measuring polarization-dependent and rotational-anisotropy optical second harmonic generation (SHG) from centrosymmetric type-II Dirac semimetal PdTe$\_2$. We found the SHG to follow C$\_{3v}$ surface symmetry with a time-varying intensity dictated by the oxidation kinetics of the material after its surface cleavage, indicating the surface origin of SHG. Quantitative characterization of the surface nonlinear susceptibility indicates a large out-of-plane response of PdTe$\_2$ with $\|\\chi\_{ccc}^{(2)}\|$ up to 25 $\\times$ 10$^{-18}$ m$^2$/V. Our results support the topological surfaces/interfaces as a new route toward applications of nonlinear optical effects with released symmetry constraints, and demonstrate SHG as a viable means to in situ study of kinetics of topological surfaces. ## Recorded benchmark results A research result applies to its stated dataset, split, metric and evaluation configuration. Compare like-for-like settings, preserve the metric's unit and direction, and distinguish paper-reported results from independent reproduction. The best result recorded here is not a claim of exhaustive, current global coverage. ## Original sources and implementation [Original paper]() [PDF]()