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On the Theory of Linear Diatomic Polymers
Author(s) -
Fedyanin V. K.,
Osipov V. A.
Publication year - 1988
Publication title -
physica status solidi (b)
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.51
H-Index - 109
eISSN - 1521-3951
pISSN - 0370-1972
DOI - 10.1002/pssb.2221470122
Subject(s) - diatomic molecule , physics , ground state , chain (unit) , soliton , quantum mechanics , boundary value problem , electron , condensed matter physics , atomic physics , nonlinear system , molecule
Abstract The model of linear diatomic polymers is considered. Both, the ground state and the phonon spectrum of a discrete AB chain are investigated. Taking into account the electron–phonon coupling as well as the finite‐band corrections, an expression for the sound velocity is derived. The continuum equations of motion in the finite‐band scheme are constructed. The kink solution is analyzed when the effects of an order of O (l/ L ), where L is a chain length, are included. It is shown that the low‐lying electronic excitations of an AB chain with fixed end atoms are the kink pairs where each kink has an irrational charge and a spin σ = 0 (or σ = 1/2). Depending on the value of the parameter α the odd‐membered chain with a free boundary is obtained to contain either a soliton or an electron–hole pair in its ground state. To compensate the irrational charge the creation of one soliton should be accompanied by a chain relaxation. In this case exactly one electron is removed from the valence band. At α = 0 all results obtained are valid for the trans‐polyacetylene model.