The role of charge and orbital order for the Verwey transition in Fe$_3$O$_4$

Magnetite, Fe$_3$O$_4$, displays a strong decrease in resistivity upon heating above $T_C=123$~K: the Verwey transition. Since long it has been proposed that charge and orbital order (CO/OO), via Fe$^{3+}$ and Fe$^{2+}$ charge disproportionation, play a crucial role. However, the mechanism behind the Verwey transition to date remains unclear. Using pump-probe O K-edge resonant soft X-ray scattering at the new LCLS SXR beamline, we have studied the role of CO/OO for the Verwey transition on ultra-fast time-scales. We focus on the structurally forbidden (00 $^1/_2$) peak. Upon excitation, the charge gap of 200~meV is quenched on resolution limited time-scales, $<250$~fs, while we still observe a residual CO/OO signal. This may indicate the existence of a new transient state of matter, displaying charge and orbital order in coexistence with metallic behavior.