Fig. 4: Transient reflectivity measurement of heat dissipation.

a Influence of repetition rate on transient reflectivity. At \(\Delta t=0\) there is a negative step in \(\Delta R/R\) as heat is introduced into the system by the pump. For \(\Delta t < 0\) we examine the influence of the previous pump pulses (see S7b for details). For the highest repetition rate, a significant residual difference in reflectivity is seen from the previous pump. For longer time delays, the influence of the previous pump reduces. Effective delay time \((\Delta {t}_{{eff}})\) for the highest (13 ns) and lowest (256 ns) repetition rates are also indicated. b Residual \(\left|\Delta R/R\right|,\) at long effective delays – extracted by averaging \(\left|\Delta R/R\right|\) between a delay of − 1 and − 0.1 ns. For effective delays over 100 ns, we still measure some influence from the previous pump pulses, indicating some heat from the pump is still present. We perform a fit, plotted with the solid red line, using a simple model that accounts for the accumulation of heat from previous pump pulses. See Methods for details. With this, we extract a decay time of 40 ± 1 ns.