Spin-dependent mass enhancement under a magnetic field in the periodic Anderson model

In order to study the mechanism underlying the mass enhancement in heavy-fermion compounds in the presence of a magnetic field, we study the periodic Anderson model by using the fluctuation exchange approximation. The resulting mass enhancement factor can have a value up to 10, which is significantly larger than that in the single-band Hubbard model. We show that the difference between the magnitude of the mass enhancement factor of up-spin (minority spin) electrons z_↑^-1 and that of down-spin (majority spin) electrons z_↓^-1 increases with the applied magnetic field B ∥ z, which is consistent with the de Haas-van Alphen measurements for CeCoIn₅, CeRu₂Si₂, and CePd₂Si₂. We predict that z_↑^-1 > z_↓^-1 in many Ce compounds, whereas z _↑^-1 < z_↓^-1 in Yb compounds.