中文摘要：

本文计及波矢q,q′声子间动力学关联效应,采用双模-压缩（声子）相干态作为再一次正则变换方案,基于Huybrechts变分近似,求解Frhlich大极化子的非经典基态.由于双模-压缩（声子）相干态导致声子相干态-压缩声子态关联效应,相干参量f～q与双模压缩角φqq′有较大幅度修正,因而显著增强了相干效应和压缩角效应.对极化子基态能量计算与分析说明在弱耦合区域,位移-声子压缩态效应的修正项ΔE（c1）与Feynman路径积分计算（ΔEf）和Huybrechts相干态修正项（ΔE0）相当.但是,声子相干态双模-压缩效应导致相应的修正（ΔE（c2））有大幅度贡献,ΔE（c2）（ΔEf,ΔE0）;在强耦合区域,位移-声子压缩态效应的修正大为减弱而可以忽略,ΔE（c1）《（ΔEf,ΔE0）.虽然声子相干态双模-压缩效应也会同时减弱,考虑到电子-声子耦合强度（α）较大,仍有ΔEc（2）（ΔEf,ΔE0）.

英文摘要：

Based on the variational approach proposed by Huybrecht,using the two-mode squeezed coherent state as the second-step canonical transformation,we have investigated the nonclassical ground state for the Frhlich polaron through considering the dynamical correlation bewteen the phonon wave vectors q and q＇.Due to the correlation effect between the phonon coherent state and the phonon squcezed state,caused by the two-mode squeezing effect of the phonon coherent state,the coherent parameter f～q and the two-mode squeezing angle φqq＇ also have a big correction correspondingly.As a result,this effect has greatly enhanced the coherent effect and the squeezing angle effect.The calculation and the analysis based on the ground state energy of the polaron have shown that 1） for the weakly coupled region,the correction ΔEc（1）due to the effect of the displaced-phonon squcezed state is comparable to the Feynma n＇ s path integral calculation（ΔEf） and the coherent state correetion by Huybrechts（ΔE0）,while the correction（ΔE（c 2）） due to the squeezing effect of the phonon coherent state has an essential contribution,i.e.ΔEc（2）（ΔEf,ΔE0）;2） for the strongly-coupled region,the contribution from the displaced-phonon squcezed state has a greatly reduction,ΔEc（1）（ΔEf,ΔE0）.Althougth,at the same time,the contribution due to the squeezing effect of the phonon coherent state also has a greatly reduction,we still have ΔEc（2）（ΔEf,ΔE0）.