  When a colloidal probe is forced through a viscoelastic fluid which is
characterized by a long stress-relaxation time, the fluid is excited out of
equilibrium. This is leading to a number of interesting effects including a
non-trivial recoil of the probe when the driving force is removed. Here, we
experimentally and theoretically investigate the transient recoil dynamics of
non-spherical particles, i.e., colloidal dumbbells. In addition to a
translational recoil of the dumbbells, we also find a pronounced angular
reorientation which results from the relaxation of the surrounding fluid. Our
findings are in good agreement with a Langevin description based on the
symmetries of a director (dumbbell) as well as a microscopic bath-rod model.
Remarkably, we find a frustrated state with amplified fluctuations when the
dumbbell is oriented perpendicular to the direction of driving. Our results
demonstrate the complex behavior of non-spherical objects within a relaxing
environment which are of immediate interest for the motion of externally but
also self-driven asymmetric objects in viscoelastic fluids.
