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We study the impact of nonhermiticity due to strong correlations in f -electron materials. One of the most remarkable phenomena occurring in nonhermitian systems is the emergence of exceptional points at which the effective nonhermitian Hamiltonian cannot be diagonalized. We here demonstrate that the temperature at which exceptional points appear around the Fermi energy is related to the Kondo temperature. For this purpose, we study the periodic Anderson model with local and nonlocal hybridization in the insulating and metallic regimes. By analyzing the effective nonhermitian Hamiltonian, which describes the single-particle spectral function, and the temperature dependence of the magnetic moment, we show that exceptional points appear at the temperature at which the magnetic moment is screened. This temperature corresponds to the Kondo temperature. These results suggest that the well-known crossover between localized and itinerant f -electrons in these materials is related to the emergence of exceptional points in the single-particle spectral function at the Fermi energy. Viewing exceptional points in the combined momentum-frequency space, we observe that the exceptional points in the effective Hamiltonian form a one-dimensional manifold which changes its structure around the Kondo temperature. arXiv:1905.12287v2 [cond-mat.str-el]

The combination of strong spin orbit coupling and strong correlations holds tremendous potential for interesting physical phenomena as well as applications in spintronics and quantum computation. In this context, we here study the interplay between the Rashba spin-orbit coupling (RSOC) and the Kondo screening in noncentrosymmetric f -electron materials. We show that the Kondo coupling of the f -electrons becomes anisotropic at high temperatures due to the RSOC. However, an isotropic Kondo effect is restored at low temperature which leads to a complete Kondo screening. We furthermore demonstrate that the Kondo effect has influence on the Rashba splitting in the band structure, which becomes temperature dependent. Although the f -electrons are localized at high temperature, a helical spin polarization of the conduction band emerges due to the scattering with the f -electrons. With decreasing temperature, the Kondo screening occurs, which leads to drastic changes in the band structure. Remarkably, these changes in the band structure depend on the helical spin polarization. For strong RSOC, we observe that the hybridization gap of one of the helical bands is closed at low temperature and a helical half-metal is formed. arXiv:1812.10888v1 [cond-mat.str-el] 28 Dec 2018 T K /D J 0 /D(=2V 2 /U) J R =0 J R =0.01 J R =0.02 J R =0.03

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