Dynamics and thermodynamics of bistable systems.

摘要

We study the dynamics and thermodynamics of nonequilibrium systems exhibiting bistability; in particular, we examine the relative stability of the two stable states and the effect of diffusion or thermal conduction on the stability of the states and the dynamics of the system. We experimentally and numerically test the thermodynamics of irreversible processes being developed by Ross, Hun, and Hunt.;We examine the relaxation dynamics of optically bistability ZnSe at the hysteresis limits and the critical point. This system has an inhomogeneous temperature distribution since it is subject to boundary conditions at the interface between the illuminated and nonilluminated regions. We find that the relaxation times of externally applied perturbations increase at both the critical point and hysteresis limits; we find critical slowing down.;We review, expand, and test the thermodynamic theory being developed by Ross, Hunt, and Hunt for systems far from equilibrium. We test a newly developed form of species-specific work, the Carnot form, for nonequilibrium thermal systems, against experiments and find it valid for the ZnSe system. We find that the Carnot results for inhomogeneous systems approach the Schlogl and experimental results as system length decreases. We also numerically test the thermodynamic theory for chemical reaction--diffusion systems on the Schlogl reaction. We examine the effect of added noise on the deterministic and stochastic formulations: the Master and Fokker-Planck equations reduce to the deterministic equation as external noise is increased.;We experimentally trace the stable and unstable stationary states in the ZnSe system. We find that the left marginal stability point is very near the equistability point. Finally, we calculate the energy dissipated in transitions from the middle branch to each of the stable branches at various input powers by experimentally measuring the temperature change. We find that over the region of bistability measured, the upper state is more stable than the lower state, indicating that the equistability point of an inhomogeneous system is near the left marginal stability point.