  By using intense coherent electromagnetic radiation, it may be possible to
manipulate the properties of quantum materials very quickly, or even induce new
and potentially useful phases that are absent in equilibrium. For instance,
ultrafast control of magnetic dynamics is crucial for a number of proposed
spintronic devices and can also shed light on the possible dynamics of
correlated phases out of equilibrium. Inspired by recent experiments on
spin-orbital ferromagnet YTiO$_3$ we consider the nonequilibrium dynamics of
Heisenberg ferromagnetic insulator with low-lying orbital excitations. We model
the dynamics of the magnon excitations in this system following an optical
pulse which resonantly excites infrared-active phonon modes. As the phonons
ring down they can dynamically couple the orbitals with the low-lying magnons,
leading to a dramatically modified effective bath for the magnons. We show this
transient coupling can lead to a dynamical acceleration of the magnetization
dynamics, which is otherwise bottlenecked by small anisotropy. Exploring the
parameter space more we find that the magnon dynamics can also even completely
reverse, leading to a negative relaxation rate when the pump is blue-detuned
with respect to the orbital bath resonance. We therefore show that by using
specially targeted optical pulses, one can exert a much greater degree of
control over the magnetization dynamics, allowing one to optically steer
magnetic order in this system. We conclude by discussing interesting parallels
between the magnetization dynamics we find here and recent experiments on
photo-induced superconductivity, where it is similarly observed that depending
on the initial pump frequency, an apparent metastable superconducting phase
emerges.
