Spin-dependent interactions in orbital-density-dependent functionals: non-collinear Koopmans spectral functionals
Creators
- 1. Scuola Internazionale Superiore di Studi Avanzati (SISSA), I-34136 Trieste, Italy
- 2. Dipartimento di Fisica, Universita' di Trieste, Strada Costiera 11, I-34151 Trieste, Italy
- 3. Laboratory for Materials Simulations, Paul Scherrer Institute (PSI), CH-5232 Villigen, Switzerland
- 4. National Centre for Computational Design and Discovery of Novel Materials (MARVEL), Paul Scherrer Institute (PSI), CH-5232 Villigen, Switzerland
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Description
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 WSe₂, the cubic perovskite CsPbBr₃, and the ferromagnetic semiconductor CrI₃. 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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References
Journal reference (Paper where the method is presented and the data discussed) A. Marrazzo, and N. Colonna, Phys. Rev. Research 6, 033085 (2024), doi: 10.1103/PhysRevResearch.6.033085
Preprint (Preprint where the data is discussed) A. Marrazzo, and N. Colonna, arXiv:2402.14575 (2024), doi: 10.48550/arXiv.2402.14575