Spin susceptibility of Anderson impurities is a key quantity in understanding the physics of Kondo screening. Traditional numerical renormalization group (NRG) calculation of the impurity contribution $chi_{textrm{imp}}$ to susceptibility, defined or
iginally by Wilson in a flat wide band, has been generalized before to structured conduction bands. The results brought about non-Fermi-liquid and diamagnetic Kondo behaviors in $chi_{textrm{imp}}$, even when the bands are not gapped at the Fermi energy. Here, we use the full density-matrix (FDM) NRG to present high-quality data for the local susceptibility $chi_{textrm{loc}}$ and to compare them with $chi_{textrm{imp}}$ obtained by the traditional NRG. Our results indicate that those exotic behaviors observed in $chi_{textrm{imp}}$ are unphysical. Instead, the low-energy excitations of the impurity in arbitrary bands only without gap at the Fermi energy are still a Fermi liquid and paramagnetic. We also demonstrate that unlike the traditional NRG yielding $chi_{textrm{loc}}$ less accurate than $chi_{textrm{imp}}$, the FDM method allows a high-precision dynamical calculation of $chi_{textrm{loc}}$ at much reduced computational cost, with an accuracy at least one order higher than $chi_{textrm{imp}}$. Moreover, artifacts in the FDM algorithm to $chi_{textrm{imp}}$, and origins of the spurious non-Fermi-liquid and diamagnetic features are clarified. Our work provides an efficient high-precision algorithm to calculate the spin susceptibility of impurity for arbitrary structured bands, while negating the applicability of Wilsons definition to such cases.
Quantum spin transport is studied in an interacting quantum dot. It is found that a conductance plateau emerges in the non-linear charge conductance by a spin bias in the Kondo regime. The conductance plateau, as a complementary to the Kondo peak, or
iginates from the strong electron correlation and exchange processes in the quantum dot, and can be regarded as one of the characteristics in quantum spin transport.
