Statistical analysis of spin switching in coupled spin-crossover molecules

We study the switching behavior of two spin-crossover molecules residing in a nanojunction device consisting of two closely spaced gold electrodes. The spin states are monitored through a real-time measurement of the resistance of the junction. A statistical analysis of the resistance values, the occupation probabilities, and the lifetimes of the respective spin states shows that the two spin-crossover molecules are coupled to each other. We extract the parameters for a minimal model describing the two coupled spin-crossover molecules. Finally, we use the time dependence of factorial cumulants to study the impact of interactions between the two spin-crossover molecules on the switching dynamics.

Figure 1

Sketch of the studied system: Two coupled spin-crossover molecules [Fe(III)(EtOSalPet)(NCS)] residing in the gap between two gold electrodes.

Figure 2

(a) Conductance as a function of time. (b) Probability density function (PDF) of the conductance values. Four different molecular states give rise to four maxima. (c) Segment of the conduction time trace from (a). Individual jumps between the conductance plateaus are visible. Lifetimes can be identified as indicated by ${\tau }_1$, ${\tau }_2$, ${\tau }_3,$ and ${\tau }_4$. The authors gratefully acknowledge reuse of the data from Ref. [26]. Copyright 2020 American Chemical Society.

Figure 3

(a)–(f) Lifetime distributions of the different states of the two-molecule system and the slowly switching molecule.

Figure 4

Stochastic system of the two molecules: The four possible states and connecting transitions.

Figure 5

(a)–(c) Factorial cumulants probing the switching dynamics of the two molecules. Experimental data are compared with the theoretical model of noninteracting (non-int.) and interacting (int.) molecules.