Extended Data Fig. 6: Distinct fluence-dependent plateau levels below and above T_N.

The photoinduced intensity plateau (p₀) of the \((\bar{3}\,3\,1)\) peak is measured as a function of incident fluence of the 260-nm pump pulse, taken at 30 K (a), 79 K (b) and 136 K (c). At 136 K, the dominant contribution to p₀ is the Debye–Waller factor. Hence, the plateau value from 136 K was subtracted at each fluence in a and b to remove the Debye–Waller effect. Green shades denote the saturation regime in which a further increase in fluence does not result in a larger p₀.