When T(LIESST) meets thermal hysteresis - a theoretical approach
Résumé
We used a macroscopic master equation for a two-level system, with simple assumptions, to calculate the kinetic behavior of a spin-crossover system when the equilibrium temperature interplays with the T(LIESST) temperature (LIESST = light-induced excited spin state trapping), that is, the thermal return temperature of the low-temperature metastable state of the system. The leading role of the unstable equilibrium branch is characterized through the crossing of the cooperative energy barrier, which induces a bifurcation of the response of the system in the strongly cooperative case. The results are shown in terms of a kinetic phase diagram, which shows the eventual discontinuities that result from the bifurcation effect. The present study suggests an experimental method for locating the unstable equilibrium branch of the thermal hysteresis, which enables determination of the equilibrium temperature of the hysteretic system, and which is not accessible by usual static measurements.