Dynamical mean-field theory for the anisotropic Kondo semiconductor : Temperature and magnetic field dependence

We investigate the periodic Anderson model with k-dependent c-f mixing reproducing the point nodes of the hybridization gap by using the dynamical mean-field theory combined with the exact diagonalization method. At low temperature below a coherence temperature T0, the imaginary part of the self-energy is found to be proportional to T 2 and the pseudogap with two characteristic energies Δ1 and Δ2 is clearly observed for T << T0, while the pseudogap is smeared with increasing T and then disappears at high temperature T > T0 due to the evolution of the imaginary self-energy. When the Coulomb interaction between f electrons U increases, Δ1, Δ2, and T0 together with Tmax at which the magnetic susceptibility is maximum decrease in proportion to the renormalization factor Z resulting in a heavy-fermion semiconductor with a large mass enhancement m∗ /m = Z -1 for large U. We also examine the effect of the external magnetic field H and find that the magnetizationM shows two metamagnetic anomalies H1 and H2 corresponding toΔ1 and Δ2 which are reduced due to the effect of H together with Z. Remarkably, Z −1 is found to be largely enhanced due to H especially for H1< H < H2, where the field induced heavy fermion state is realized. The obtained results seem to be consistent with the experimental results observed in the anisotropic Kondo semiconductors such as CeNiSn