  A theoretical study on the dynamics of an antiferromagnetic (AFM) skyrmion is
indispensable for revealing the underlying physics and understanding the
numerical and experimental observations. In this work, we present a reliable
theoretical treatment of the spin current induced motion of an AFM skyrmion in
the absence and presence of pinning defect. For an ideal AFM system free of
defect, the skyrmion motion velocity as a function of the intrinsic parameters
can be derived, based on the concept that the skyrmion profile agrees well with
the 360 domain wall formula, leading to an explicit description of the skyrmion
dynamics. However, for an AFM lattice containing a defect, the skyrmion can be
pinned and the depinning field as a function of damping constant and pinning
strength can be described by the Thiele approach. It is revealed that the
depinning behavior can be remarkably influenced by the time dependent
oscillation of the skyrmion trajectory. The present theory provides a
comprehensive scenario for manipulating the dynamics of AFM skyrmion,
informative for future spintronic applications based on antiferromagnets.
