NONLINEAR SELF-TRAPPING IN A QUANTUM DIMER

The Frohlich-Einstein dimer (FED) is a dynamical system of four coupled oscillators which is nonlinear if described in terms of classical physics. Based on the Frohlich Hamiltonian of solid state physics, the FED model gives rise to a type of energy localization that is featured in Davydov's theory of protein solitons. Recent analytical results are presented here which give an improved quantum-mechanical description of local mode dynamics in the FED. The qualitative picture of localization dynamics obtained from these results is compared with descriptions obtained from approximation methods commonly used in studies of more complicated systems. The FED model is shown to be particularly suitable for such comparative studies.