通过低维碲的多形性和维度限域调控激子
Engineering Excitons through Polymorphism and Dimensional Confinement in Low-Dimensional Tellurium
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中文总结 AI 辅助
本文通过GW+BSE方法，研究低维碲的激子特性，发现不同维度、多形相的碲具有不同激子行为，揭示强电子-空穴关联可与非平凡带拓扑兼容，为调控激子提供了新途径。
中文摘要 AI 辅助
维度、带边电子结构与电子-空穴相互作用的相互作用决定了低维碲的光学响应，但其激子行为的微观起源在很大程度上仍未被探索。本文采用多体GW方法和Bethe-Salpeter方程，研究二维碲多形相和一维螺旋纳米线的准粒子、激子及光学性质。结果表明，激子响应强烈依赖于带边色散、晶体对称性和维度限域：α-碲烯呈现相对较弱且空间扩展的电子-空穴关联；而β-碲烯由自旋轨道耦合（SOC）诱导的准平带边态，产生了强束缚且各向异性的近红外激子。动量分辨的BSE本征向量和实空间激子波函数直接揭示了这些激子态截然不同的局域化特性与各向异性。值得注意的是，此前被确定为具有Z₂=1的量子自旋霍尔相的氢钝化六方碲烯，其直接激子结合能可达0.51 eV，且具有紧凑且近各向同性的面内激子分布，这表明强电子-空穴关联与非平凡带拓扑完全兼容，同时激子的结合强度和空间特性仍强烈依赖于基础带边电子结构与晶体对称性。一维螺旋纳米线代表强限域极限，呈现高直接激子结合能，且光学响应明显向紫外区域偏移。
英文摘要
The interplay between dimensionality, band-edge electronic structure, and electron-hole interactions governs the optical response of low-dimensional tellurium, yet the microscopic origin of its excitonic behavior remains largely unexplored. Here, we investigate the quasiparticle, excitonic, and optical properties of two-dimensional tellurium polymorphs and one-dimensional helical nanowires using many-body GW and the Bethe--Salpeter equation. Our results reveal a strong dependence of the excitonic response on band-edge dispersion, crystal symmetry, and dimensional confinement. $α$-tellurene exhibits comparatively weak and spatially extended electron-hole correlations, whereas the SOC-induced quasi-flat band-edge states of $β$-tellurene give rise to a strongly bound and anisotropic near-infrared exciton. Momentum-resolved BSE eigenvectors and real-space exciton wave functions directly reveal the contrasting localization and anisotropy of these excitonic states. Remarkably, hydrogen-passivated hexagonal tellurene, previously identified as a quantum spin Hall phase with $Z_2=1$, supports an even larger direct exciton binding energy of 0.51 eV together with a compact and nearly isotropic in-plane excitonic distribution. This demonstrates that strong electron-hole correlations are fully compatible with nontrivial band topology, while the binding strength and spatial character of the exciton remain strongly dependent on the underlying band-edge electronic structure and crystal symmetry. The one-dimensional helical nanowire represents the strong-confinement limit, exhibiting a direct high exciton binding energy and a pronounced shift of the optical response toward the ultraviolet.
