%A Luo Zhi-Hua, Cao Xi-Jin, Yu Chao-Fan
%T Properties of ground state and anomalous quantum fluctuations in one-dimensional polaron–soliton systems—the effects of electron-two-phonon interaction and non-adiabatic quantum correlations
%0 Journal Article
%D 2011
%J Chin. Phys. B
%R 10.1088/1674-1056/20/6/067103
%P 67103-067103
%V 20
%N 6
%U {http://cpb.iphy.ac.cn/CN/abstract/article_26233.shtml}
%8 2011-06-15
%X Based on the Holstein model Hamiltonian of one-dimensional molecular crystals, by making use of the expansion approach of the correlated squeezed-coherent states of phonon instead of the two-phonon coherent state expansion scheme, the properties of the ground state and the anomalous quantum fluctuations are investigated in a strongly coupled electron-phonon system with special consideration of the electron-two-phonon interaction. The effective renormalization (*ã*_{i}) of the displacement of the squeezed phonons with the effect of the squeezed-coherent states of phonon and both the electron-displaced phonon and the polaron-squeezed phonon correlations have been combined to obtain the anomalous quantum fluctuations for the corrections of the coherent state. Due to these non-adiabatic correlations, the effective displacement parameter *ã*_{i} is larger than the ordinary parameter *α*_{i}^{(0)}. In comparison with the electron-one-phonon interaction *(g)* corrected as *ã*_{i}, we have found the electron-two-phonon interaction (*g*_{1}) corrected as *ã*_{i}^{2}*g*_{1} is enhanced significantly. For this reason, the ground state energy (*E*_{0}^{(2)}) contributed by the electron-two-phonon interaction is more negative than the single-phonon case (*E*_{0}^{(1)}) and the soliton solution is more stable. At the same time, the effects of the electron-two-phonon interaction greatly increase the polaron energy and the quantum fluctuations. Furthermore, in a deeper level, we have considered the effect of the polaron-squeezed phonon correlation (*f*-correlation). Since this correlation parameter *f*>1, this effect will strengthen the electron-one and two-phonon interactions by *fã*_{i}g and *f*^{2}ã_{i}^{2}g_{1}, respectively. The final results show that the ground state energy and the polaron energy will appear more negative further and the quantum fluctuations will gain further improvement.