Bound states of tunneling electrons in molecular chains

We have studied the bound states of the extra electron in a molecular chain corresponding to the physical situation of the electron tunneling through the system. The bound-state spectrum is obtained using the formalism of the multiple scattering theory MST . The subbarrier scattering operators, the fundamental building blocks of MST, are evaluated within the variational asymptotic method which explicitly takes into account the many-electron interactions of the tunneling electron with the electrons of the scattering center. We have shown that the energy spectrum of the bound states of the tunneling electron in a linear chain of three-dimensional scattering centers substantially deviates from the spectrum of independent single-electron states of Bloch electrons in a system described by a single-electron effective potential. In particular, the number of states in the band can be less than the number of centers of the chain. These states form two bands instead of a single band and the bands exhibit nonanalytical, square root dispersion − m k−km in the vicinity of the point km where both bands come together. These findings are important for developing a physically viable theory of electron tunneling in single molecular systems.