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oe1(光电查) - 科学论文

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?? 中文（中国） ▾

  • Two-dimensional honeycomb borophene oxide: strong anisotropy and nodal loop transformation

    摘要： The search for topological semimetals is mainly focused on heavy-element compounds by following the footsteps of previous research on topological insulators, with less attention on light-element materials. However, the negligible spin orbit coupling with light elements may turn out to be beneficial for realizing topological band features. Here, using first-principles calculations, we propose a new two-dimensional light-element material—the honeycomb borophene oxide (h-B2O), which has nontrivial topological properties. The proposed structure is based on the recently synthesized honeycomb borophene on an Al (111) substrate [W. Li, L. Kong, C. Chen, J. Gou, S. Sheng, W. Zhang, H. Li, L. Chen, P. Cheng and K. Wu, Sci. Bull., 2018, 63, 282–286]. The h-B2O monolayer is completely flat, unlike the oxides of graphene or silicene. We systematically investigate the structural properties of h-B2O, and find that it has very good stability and exhibits significant mechanical anisotropy. Interestingly, the electronic band structure of h-B2O hosts a nodal loop centered around the Y point in the Brillouin zone, protected by the mirror symmetry. Furthermore, under moderate lattice strain, the single nodal loop can be transformed into two loops, each penetrating through the Brillouin zone. The loops before and after the transition are characterized by different Z × Z topological indices. Our work not only predicts a new two-dimensional material with interesting physical properties, but also offers an alternative approach to search for new topological phases in 2D light-element systems.

    关键词： borophene oxide,light-element materials,topological semimetals,nodal loop,mechanical anisotropy

    更新于2025-09-19 17:15:36

  • Free-carrier dynamics in Au <sub/>2</sub> Pb probed by optical conductivity measurements

    摘要： We measured the optical reflectivity of the Dirac material Au2Pb in a broad frequency range (30–48 000 cm?1) for temperatures between 9 and 300 K. The optical conductivity, computed from the reflectivity, is dominated by free-carrier contributions from topologically trivial bulk bands at all temperatures. The temperature-independent total plasma frequency of these carriers is 3.9 ± 0.2 eV. Overall, optical response of Au2Pb is typically metallic with no signs of localization and bad-metal behavior.

    关键词： topological semimetals,optical conductivity,Dirac materials

    更新于2025-09-10 09:29:36

  • <i>Ab initio</i> optical and energy loss spectra of transition metal monopnictides TaAs, TaP, NbAs, and NbP

    摘要： Transition metal monopnictides represent a new class of topological semimetals with low-energy excitations, namely, Weyl fermions. We report optical properties across a wide spectral energy range for TaAs, TaP, NbAs, and NbP, calculated within density functional theory. Spectra are found to be somewhat independent of the anion and the light polarization. Their features are explained in terms of the upper s, p, d, and f electrons. Characteristic absorption features are related to the frequency dependence of the Fresnel re?ectivity. While the lower part of the energy loss spectra is dominated by plasmonic features, the high-energy structures are explained by interband transitions.

    关键词： Topological semimetals,Energy loss spectra,Optical properties,Transition metal monopnictides,Weyl fermions

    更新于2025-09-09 09:28:46

  • All-Silicon Topological Semimetals with Closed Nodal Line

    摘要： Owing to the natural compatibility with current semiconductor industry, silicon allotropes with diverse structural and electronic properties provide promising platforms for the next-generation Si-based devices. After screening 230 all-silicon crystals in the zeolite frameworks by first-principles calculations, we disclose two structurally stable Si allotropes (AHT-Si24 and VFI-Si36) containing open channels as topological node-line semimetals with Dirac nodal points forming a nodal loop in the kz=0 plane of Brillouin zone. Interestingly, their nodal loops protected by inversion and time-reversal symmetries are robust against SU(2) symmetry breaking due to very weak spin-orbit coupling of Si. When the nodal lines are projected onto the (001) surface, flat surface bands can be observed because of the nontrivial topology of the bulk band structures. Our discoveries extend the topological physics to the three-dimensional Si materials, highlighting the possibility to realize low-cost, nontoxic and semiconductor-compatible Si-based electronics with topological quantum states.

    关键词： Zeolite frameworks,Node-line semimetals,Topological semimetals,Silicon allotropes,First-principles calculations

    更新于2025-09-04 15:30:14

  • PT symmetry protected non-Hermitian topological systems

    摘要： We study PT symmetry protected topological phase in non-Hermitian 1D and 2D systems. We show that topological phase exist in non-Hermitian PT symmetric systems for both gapped and gapless systems and discuss appearance of exceptional points. We apply our formalism to a complex extension of the SSH model, topological semimetals and nodal superconductors.

    关键词： SSH model,nodal superconductors,non-Hermitian systems,topological semimetals,PT symmetry,topological phase

    更新于2025-09-04 15:30:14