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Transport of quantum excitations coupled to spatially extended nonlinear many-body systems

Iubini, S. I. ; Kerans, O. ; Omar, Y. ; Piazza, F.

New Journal of Physics Vol. 17, Nº NA, pp. 113030 - NA, November, 2015.

ISSN (print): 1367-2630
ISSN (online):

Journal Impact Factor: 3,558 (in 2014)

Digital Object Identifier: 10.1088/1367-2630/17/11/113030

Abstract
The role of noise in the transport properties of quantum excitations is a topic of great importance in many fields, from organic semiconductors for technological applications to light-harvesting complexes in photosynthesis. In this paper we study a semi-classical model where a tight-binding Hamiltonian is fully coupled to an underlying spatially extended nonlinear chain of atoms. We show that the transport properties of a quantum excitation are subtly modulated by (i) the specific type (local versus non-local) of exciton–phonon coupling and by (ii) nonlinear effects of the underlying lattice. We report a non-monotonic dependence of the exciton diffusion coefficient on temperature, in agreement with earlier predictions, as a direct consequence of the lattice-induced fluctuations in the hopping rates due to long-wavelength vibrational modes. A standard measure of transport efficiency confirms that both nonlinearity in the underlying lattice and off-diagonal exciton–phonon coupling promote transport efficiency at high temperatures, preventing the Zeno-like quench observed in other models lacking an explicit noise-providing dynamical system.