The polaron - bipolaron transition for acoustical three-dimensional polarons
The polaron - bipolaron transition for acoustical three-dimensional polarons
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声学三维极化子的极化子-双极化子转变
DOI：
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发表时间：
1996
期刊：
影响因子：
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通讯作者：
F. Peeters
中科院分区：
文献类型：
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作者：
W. B. Costa;F. Peeters
本文用费曼路径积分法研究了三维双极化子的基态能量。声学极化子表现出从准自由态到自俘获态的过渡。根据声子波向量空间中的德拜截止值，这种转换可以是连续的或不连续的。如果有两个电子存在，第二次跃迁就成为可能：跃迁到双极化子态，在这种状态下，两个电子在同一位置周围被自困。相应的相图被计算为截止、电子-声子耦合强度和电子之间的斥力(U)的函数。我们发现：(1)双极化子跃迁是一阶跃迁；（ii）两个极化子之间也有可能处于准自由状态，即不自困；(3)有效粒子质量在过渡点处大幅增加。
The ground-state energy of an acoustical bipolaron in three dimensions (3D) is studied within the Feynman path integral method. The acoustical polaron exhibits a transition from the quasi-free state to the self-trapped state. Depending on the value of the Debye cut-off in phonon wavevector space this transition can be continuous or discontinuous. If two electrons are present a second transition becomes possible: the transition to the bipolaron state in which the two electrons are self-trapped around the same position. The corresponding phase diagram is calculated as function of the cut-off , the electron - phonon coupling strength , and the repulsion (U) between the electrons. We found that: (i) the bipolaron transition is a first-order transition; (ii) it is also possible between two polarons which are in the quasi-free state, i.e. are not self-trapped; and (iii) the effective particle mass increases substantially at the transition point.