  The study of photoexcited strongly correlated materials is attracting growing
interest since their rich phase diagram often translates into an equally rich
out-of-equilibrium behavior, including non-thermal phases and photoinduced
phase transitions. With femtosecond optical pulses, electronic and lattice
degrees of freedom can be transiently decoupled, giving the opportunity of
stabilizing new states of matter inaccessible by quasi-adiabatic pathways. Here
we present a study of the ultrafast non-equilibrium evolution of the prototype
Mott-Hubbard material V2O3, which presents a transient non-thermal phase
developing immediately after photoexcitation and lasting few picoseconds. For
both the insulating and the metallic phase, the formation of the transient
configuration is triggered by the excitation of electrons into the bonding a1g
orbital, and is then stabilized by a lattice distortion characterized by a
marked hardening of the A1g coherent phonon. This configuration is in stark
contrast with the thermally accessible ones - the A1g phonon frequency actually
softens when heating the material. Our results show the importance of selective
electron-lattice interplay for the ultrafast control of material parameters,
and are of particular relevance for the optical manipulation of strongly
correlated systems, whose electronic and structural properties are often
strongly intertwinned.
