Relationship between exceptional points and the Kondo effect in f-electron materials

We study the impact of non-Hermiticity due to strong correlations in f -electron materials. One of the most remarkable phenomena occurring in non-Hermitian systems is the emergence of exceptional points at which the effective non-Hermitian 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 non-Hermitian 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.