Magnetically Robust Multipole Kondo Effect

In order to promote our understanding on magnetically robust heavy-fermion phenomenon observed in Sm-based filled skutterudites, we focus on Kondo-like behavior due to multipole degree of freedom. By employing a numerical renormalization group method, we evaluate the Sommerfeld coefficient gamma of electronic specific heat of a seven-orbital Anderson model with five f electrons corresponding to Sm3+ ion under a magnetic field H. From the numerical results, we discuss the dependence of gamma on H for (0, 0, 1), (1, 1, 0), and (1, 1, 1) directions. It is observed in common that gamma is eventually independent of H for large magnitude of H. Note, however, that for (1, 1, 1) direction, we find a sharp increase of gamma around at 11 Tesla, which may be a signal for the relevance of xyz octupole moment.