科研之友
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摘要
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 T-0, the imaginary part of the self-energy is found to be proportional to T-2 and the pseudogap with two characteristic energies (Delta) over tilde (1) and (Delta) over tilde (2) is clearly observed for T %26lt;%26lt; T-0, while the pseudogap is smeared with increasing T and then disappears at high temperature T greater than or similar to T-0 due to the evolution of the imaginary self-energy. When the Coulomb interaction between f electrons U increases, (Delta) over tilde (1), (Delta) over tilde (2), and T-0 together with T-max 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 mm = Z(-1) for large U. We also examine the effect of the external magnetic field H and find that the magnetization M shows two metamagnetic anomalies H-1 and H-2 corresponding to (Delta) over tilde (1) and (Delta) over tilde (2) 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 H-1 less than or similar to H less than or similar to H-2, 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.
- 出版日期2012-4-9
