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Nonlinear optical response of a two-dimensional semi-Dirac system in terahertz regime
摘要： We demonstrate a strong nonlinear optical response in a two-dimensional semi-Dirac system in the terahertz regime. By applying the Boltzmann transport theory for the intra-band process and a quantum mechanics method for the inter-band process, we obtained the three-photon current response. It is found that both the intra- and inter-band excitations make significant contributions to the nonlinear response. The third order conductivities (TOCs) σyy(3) are about two magnitudes higher than that of σxx(3). Interestingly, for the inter-band TOCs, there is a sign change when the chemical potential varies across the saddle point in the conduction band in kx direction (that is parabolic), due to the competition between the two opposite nonlinear current contributed by the electrons at states k > kD and k < kD, respectively. Finally, we show that the nonlinear response in terahertz regime is significant at experimentally accessible field strengths. Our results suggest that this system could be of potential applications in photonic device for frequency up-conversion.
关键词： black phosphorous,semi-Dirac system,nonlinear optical response,Boltzmann transport theory
更新于2025-09-23 15:22:29
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[NanoScience and Technology] Silicene (Prediction, Synthesis, Application) || Electronic and Topological Properties of Silicene, Germanene and Stanene
摘要： In this chapter, we review the recent progress on electronic and topological properties of monolayer topological insulators including silicene, germanene and stanene. We start with the description of the topological nature of the general Dirac system and then apply it to silicene by introducing the spin and valley degrees of freedom. Based on them, we classify all topological insulators in the general honeycomb system. We discuss topological electronics based on honeycomb systems. We introduce the topological Kirchhoff law, which is a conservation law of topological edge states. Field effect topological transistor is proposed based on the topological edge states. We show that the conductance is quantized even in the presence of random distributed impurities. Monolayer topological insulators will be a key for future topological electronics and spin-valleytronics.
关键词： topological Kirchhoff law,silicene,topological insulators,topological electronics,Dirac system,field effect topological transistor,spin and valley degrees of freedom,stanene,quantized conductance,germanene
更新于2025-09-23 15:21:21
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[IEEE 2019 44th International Conference on Infrared, Millimeter, and Terahertz Waves (IRMMW-THz) - Paris, France (2019.9.1-2019.9.6)] 2019 44th International Conference on Infrared, Millimeter, and Terahertz Waves (IRMMW-THz) - Strong Anisotropic Photo-mixing Effect of Semi-Dirac Materials in the Terahertz Regime
摘要： Semi-Dirac materials such as a TiO2/VO2 have been shown to possess a parabolic energy-momentum dispersion in the x direction and linear dispersion in the y direction. This unique energy-momentum dispersion leads to many anisotropic effects. Here, we demonstrate a strong anisotropic photo-mixing effect in such systems which can be used to control the strength of the photo-response.
关键词： semi-Dirac system,momentum dispersion,anisotropic photo-mixing effect,terahertz regime
更新于2025-09-16 10:30:52