Two-Particle Excitations of the Kondo Insulator around the Critical Point

The spin and the charge excitations of the Kondo insulator are investigated based on the periodic Anderson model at half-filling.We employ the self-consistent fluctuation approximation, where the two-particle correlation functions and the effective irreducible vertices are determined self-consistently to satisfy the Pauli principle. When the system approaches the antiferromagnetic critical point with the strong electron correlation, the spin excitation spectrum is enhanced while the charge excitation spectrum is suppressed. The characteristic energy of the spin excitation is more strongly renormalized than that of the charge one.

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