Evidence for inhomogeneous and percolative dynamics across the photo-induced insulator-metal phase transition in Ca3Ru2O7

Upon intense femtosecond photo-excitation, a many-body system can undergo a phase transi-

tion through a non-equilibrium pathway, but understanding these pathways remains an outstanding

challenge. Here, we use time-resolved second harmonic generation to investigate a photo-induced

insulator-metal transition in Ca3Ru2O7 and show that mesoscale inhomogeneity profoundly influ-

ences the transition dynamics. We observe a marked slowing down of the characteristic time, τ , that

quantifies the transition from the insulating to the metallic state. τ evolves non-monotonically as a

function of photo-excitation fluence, first increasing from below 200 fs to ∼1.4 ps, and then decreas-

ing to below 200 fs. To account for the experimentally observed behavior, we perform a simulation

using a statistical model that demonstrates how the percolation and coarsening of metallic clusters

governs the transition kinetics. Our work highlights the importance of mesoscale inhomogeneity in

the dynamics of photo-induced insulator-metal phase transitions and provides a model that may be

useful for understanding such transitions more broadly.