Charged ultradiscrete supersonic kinks and discrete breathers in nonlinear molecular chains with realistic interatomic potentials and electron-phonon interactions

Abstract

The problem of electron or hole trapping by supersonic lattice kink is revisited. Supersonic kinks in molecular chains with realistic interatomic potential produce local compression of the lattice. Lattice compression enhances electron Fermi energy and therefore produces for the electron a local potential hill, rather than a potential well, through the deformation potential of the proper sign. Here we discuss the possibility of electron trapping above the top of its tight-binding conduction band, where it possesses negative effective mass, by supersonic kink in a molecular chain with realistic interatomic potentials and electron-phonon interactions. The localization length of the electron wave function is much larger than lattice period in the case of adiabatic electron dynamics and decreases with the velocity of the ultradiscrete supersonic kink with the approximately sinusoidal envelope with the “magic” wave number. Such kinks were revealed in lattices with different interatomic potentials with hardening anharmonicity. Electron or hole can also be trapped by discrete breather (intrinsic localized mode) in the lattice with realistic asymmetric anharmonic potential. The local quasi-static strain, produced by the stationary or slowly-moving discrete breather in the lattice, can trap the electron (or hole) with its localization below the lower edge of the conduction (or above the upper edge of the valence) band.