  Magnetic skyrmions are prime candidates for future spintronic devices.
However, incorporating them as an entity for information technology hinges on
their interaction with defects ubiquitous to any device. Here we map from
first-principles, the energy-profile of single skyrmions interacting with
single-atom impurities, establishing a generic shape as function of the
defect's electron filling. Depending on their chemical nature, foreign 3d and
4d transition metal adatoms or surface-implanted defects can either repel or
pin skyrmions in PdFe/Ir(111) thin films, which we relate to the degree of
filling of bonding and anti-bonding electronic states inherent to the proximity
of the non-collinear magnetic structure. Similarities with key concepts of bond
theories in catalysis and surface sciences imbue the universality of the shape
of the interaction profile and the potential of predicting its interaction. The
resulting fundamental understanding may give guidance for the design of devices
with surface-implanted defects to generate and control skyrmions.
