We study the Hamiltonian dynamics of a free particle injected onto a chain containing a periodic array of harmonic oscillators in thermal equilibrium. The particle interacts locally with each oscillator, with an interaction that is linear in the oscillator coordinate and independent of the particle's position when it is within a finite interaction range. At long times the particle exhibits diffusive motion, with an ensemble averaged mean-squared displacement that is linear in time. The diffusion constant at high temperatures follows a power law D~T 5/2 for all parameter values studied. At low temperatures particle transport changes to a hopping process in which the particle is bound for considerable periods of time to a single oscillator before it is able to escape and explore the rest of the chain. A different power law, D~T 3/4, emerges in this limit. A thermal distribution of particles exhibits thermally activated diffusion at low temperatures as a result of classically self-trapped polaronic states.
A. A. Silvius et al., "Adiabatic-nonadiabatic Transition in the Diffusive Hamiltonian Dynamics of a Classical Holstein Polaron," Physical Review B, American Physical Society (APS), Jan 2006.
The definitive version is available at http://dx.doi.org/10.1103/PhysRevB.73.014304
National Science Foundation (U.S.)
Keywords and Phrases
Diffusion; Harmonic oscillators; Hopping conduction; Polarons
Article - Journal
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