Magnetic field dependence of the specific heat of a heavy Fermion system

One of the distinguishing characteristics of heavy Fermion materials is the extraordinarily large size of the electronic specific heat at low temperatures. It is also observed that in some cases, the specific heat is reduced drastically by an external magnetic field. We show that this behavior can be simulated by using the non-degenerate lattice Anderson model on a 4-site tetrahedral cluster. Interactions included in the model are the on-site Couloumb repulsion between electrons in the f-orbital and the off-site spin conserving hybridization between electrons in the conduction and the f-orbitals. Our calculation is done by using the exact diagonalization method.;This calculation shows that the enormous size of the electronic specific heat is due to the many states lying near the ground state which are mostly spin rearrangements of the f-electrons. The suppression of the specific heat in the presence of an external magnetic field is due to the lifting of the degeneracy in the energy levels which are consequently ordered according to spin. Our results are to yield qualitative agreement compared with experiments on CeCu...