  We consider the screening of an impurity moment in a d-wave superconductor
under the influence of a Zeeman magnetic field. Using the Numerical
Renormalization Group technique, we investigate the resulting pseudogap Kondo
problem, in particular the field-induced crossover behavior in the vicinity of
the zero-field boundary quantum phase transition. The impurity spectral
function and the resulting changes in the local host density of states are
calculated, giving specific predictions for high-field STM measurements on
impurity-doped cuprates.
