| Title | Electronic Structure and Nonlinear Optical Properties of NbIrTe4 with First- Principles Method |
|---|---|
| ID_Doc | 33817 |
| Authors | Xu, YJ; Yang, L; Deng, XH; Yun, S |
| Title | Electronic Structure and Nonlinear Optical Properties of NbIrTe4 with First- Principles Method |
| Year | 2024 |
| Published | Acta Optica Sinica, 44.0, 16 |
| Abstract | Objective Terahertz waves have emerged as a focal point in contemporary scientific research due to their unique physical properties. The distinctive region of the waveband exhibits characteristics such as low energy and easy absorption by the atmospheric environment, posing considerable technical challenges to terahertz detection technology-a -a core technology in this domain. Particularly at room temperature, there are numerous constraints related to photosensitive materials for detection, device sensitivity, response speed, and technical cost. This paper focuses on the study of topological semimetal materials and performs calculations on the electronic structure and nonlinear optical properties of the Weyl semimetal NbIrTe4. 4 . The research indicates that based on the gapless topological band structure, Weyl semimetals can not only detect terahertz radiation but also generate photocurrents, thus holding promise for efficient terahertz detection at room temperature. This study aims to predict the terahertz detection potential of NbIrTe4 4 through systematic research and analysis, providing a scientific foundation for exploring efficient terahertz photosensitive materials, thereby advancing innovation in terahertz detection technology and fostering its broad application across various practical fields. Methods This study initially employs the finite displacement method to analyze the phonon spectrum of NbIrTe4, 4 , confirming its dynamical stability. Subsequently, the complex topological band structure of this Type II Weyl semimetal NbIrTe4 4 is meticulously examined using first- principle calculations, revealing special surface states and Fermi arc states on the (001) plane with the aid of the surface Green's function method. Finally, by investigating the bulk photovoltaic effect at low frequencies via the method of maximally localized Wannier functions, the photovoltaic response of the material is elucidated through an analysis of the conductivity tensor of displacement current allowed by symmetry, with a particular emphasis on its optical response in the terahertz frequency range. Results and Discussions In analyzing the surface state calculation results for NbIrTe4, 4 , we unveil the strong dependence of its peculiar topological surface states and the connectivity of the surface Fermi arcs on the type of surface termination (Fig. 4). In studying its nonlinear optical properties, we precisely calculate the conductivity tensor of displacement current for its bulk photovoltaic effect-a result yet to be achieved in density functional theory calculations. Our findings demonstrate that at specific frequencies, the conductivity tensor of displacement current of NbIrTe4 4 is significantly pronounced, with several independent components allowed by symmetry reaching peak values in the terahertz frequency range (Fig. 6), exceeding those of typical materials by more than an order of magnitude and comparable to the response of Type I Weyl semimetals. This suggests that the enhancement of the displacement current is intimately linked to the properties of the Weyl points. Conclusions Through first- principles calculations, this study comprehensively resolves the unique energy- band structure of the Type II Weyl semimetal NbIrTe4, 4 , identifying it as a highly stable Weyl semimetal phase. The surface characteristics of the material display distinctive surface Fermi arcs, and we reveal that the connectivity of its surface Fermi arcs is influenced by the type of surface termination. When examining the bulk photovoltaic effect of the non-- centrosymmetric material NbIrTe4, 4 , an exceptional photoelectric response in the terahertz domain is discovered. Owing to the material's anisotropy and symmetry influences, different photoelectric response of the conductivity tensor of displacement current emerges. Near terahertz frequencies, the peak value of the conductivity tensor component of displacement current reaches up to 407.32 mu A/V2, 2 , benefiting from the novel topological states of carriers around the Weyl points. These significant findings provide scientific evidence for the immense potential of employing NbIrTe4 4 as an efficient terahertz photo- detection material and provide robust theoretical support and guidance for the development of future high-- performance terahertz photosensitive materials. |
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