  In this work we fabricate and characterize a functionalized superconducting
(SC) Nb tip of a scanning tunnelling microscope (STM). The tip is
functionalized with a Tetracyanoquinodimethane molecule (TCNQ) that accepts
charge from the tip and develops a magnetic moment. As a consequence, in
scanning tunnelling spectroscopy (STS), sharp, bias symmetric sub-gap states
identified as Yu-Shiba-Rusinov (YSR) bound states appear against the
featureless density of states of a metallic gr/Ir(111) sample. Although the
coupling regime of the magnetic impurity with the SC tip depends on the initial
absorption configuration of the molecule, the interaction strength between the
superconducting tip and the charged TCNQ molecule can be reversibly controlled
by tuning the tip-sample distance. The controlled transition from one coupling
regime to the other allows us to verify the relation between the energy scales
of the two competing many-body effects for the functionalized tip. Quenching
the SC state of the Nb tip with a magnetic field switches abruptly from a tip
dominated by the YSR bound states to a Kondo tip.
