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arXiv 2402.14575cond-mat.mtrl-sci
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轨道密度依赖泛函中的自旋依赖相互作用:非共线 Koopmans 谱泛函

Spin-dependent interactions in orbital-density-dependent functionals: non-collinear Koopmans spectral functionals

Antimo Marrazzo, Nicola Colonna

AI总结:

本文基于 Wannier 函数和密度泛函微扰理论开发了非共线 Koopmans-compliant 谱泛函,在准粒子近似下准确预测了自旋轨道耦合材料的能带结构,自然包含了标准多体微扰理论中需复杂修正才能获得的自旋依赖相互作用和屏蔽效应。

摘要:

自旋轨道耦合或非共线磁性自旋态的存在会对材料的基态和光谱性质产生显著影响,特别是对能带结构。在此,我们基于 Wannier 函数和密度泛函微扰理论开发了非共线 Koopmans-compliant 泛函,旨在准粒子近似下获得精确的光谱性质。我们的非共线 Koopmans-compliant 理论涉及四分量轨道密度的泛函,可由 Wannier 函数的电荷与自旋矢量密度获得。我们在四种代表性的非磁和磁性半导体上验证了该方法,其自旋轨道耦合效应从小到大不等:III-IV 族半导体 GaAs、过渡金属二硫族化合物 WSe$_2$、立方钙钛矿 CsPbBr$_3$ 以及铁磁半导体 CrI$_3$。预测的带隙精度与最先进的多体微扰理论相当,并包含了基于随机相位近似标准图解方法中缺失的自旋依赖相互作用和屏蔽效应。在多体微扰理论中引入轨道和自旋依赖相互作用需自屏蔽或顶点修正,而在 Koopmans 泛函框架中它们自然涌现。

英文摘要:

The presence of spin-orbit coupling or non-collinear magnetic spin states can have dramatic effects on the ground-state and spectral properties of materials, in particular on the band structure. Here, we develop non-collinear Koopmans-compliant functionals based on Wannier functions and density-functional perturbation theory, targeting accurate spectral properties in the quasiparticle approximation. Our non-collinear Koopmans-compliant theory involves functionals of four-component orbitals densities, that can be obtained from the charge and spin-vector densities of Wannier functions. We validate our approach on four emblematic non-magnetic and magnetic semiconductors where the effect of spin-orbit coupling goes from small to very large: the III-IV semiconductor GaAs, the transition-metal dichalcogenide WSe$_2$, the cubic perovskite CsPbBr$_3$, and the ferromagnetic semiconductor CrI$_3$. The predicted band gaps are comparable in accuracy to state-of-the-art many-body perturbation theory and include spin-dependent interactions and screening effects that are missing in standard diagrammatic approaches based on the random phase approximation. While the inclusion of orbital- and spin-dependent interactions in many-body perturbation theory requires self-screening or vertex corrections, they emerge naturally in the Koopmans-functionals framework.

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