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

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 becomes non-diagonalizable. We here demonstrate that Kondo temperature is related to the temperature at which exceptional points appear around the Fermi level. 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 screening of the magnetic moment, from which the Kondo temperature can be found, we show that exceptional points appear at the temperature at which the magnetic moment is screened. These results suggest that the well-known crossover between localized and itinerant f electrons in $f$-electron materials is related to the emergent exceptional points in the single-particle spectral function.