Bridge-mediated Donor-Acceptor Effective Coupling: Exact theoretical description

TL;DR

This paper derives an exact formula for bridge-mediated donor-acceptor effective coupling in quantum systems, highlighting its relation to Hamiltonian eigenvalues and comparing it with perturbative methods.

Contribution

It provides a precise, non-perturbative expression for effective coupling in tight-binding models, improving understanding over previous approximate approaches.

Findings

Exact expression for effective coupling derived

Comparison shows limitations of perturbative methods

Highlights importance of eigenenergy level spacings

Abstract

An exact expression of the bridge-mediated donor-acceptor effective coupling, is derived. For systems represented by a tight-binding Hamiltonian with nearest-neighbor interactions, we show that the effective coupling, is equal to the product over all square of nearest-neighbor couplings divided by an appropriate product of level spacing of eigen energies of the Hamiltonian. Results of this calculation are compared to those obtained by perturbative approaches and some drawbacks of the latter are pointed out.