极化子范例：双耦合有效带模型
The polaron paradigm: a dual coupling effective band model
摘要：
玻色子浴的非对角耦合完全改变了极化动力学，从通常的对角耦合模式的平滑变化的属性。我们研究，使用分析和数值方法，一个模型，既有对角荷斯坦和非对角苏-施里弗-希格（SSH）耦合。先前在纯SSH模型中发现的临界耦合，即$k=0$有效质量发散的临界耦合，现在变成了耦合常数平面中的一条过渡线--该线的形式取决于绝热性参数。详细的结果给出了准粒子和基态的属性，在很宽的范围内的耦合和绝热比。新的范式涉及到一个不稳定，在过渡线，简单的荷斯坦极化子到一个有限的基态动量，但到处都是一个不断演变的带形。在这些模型中，都不存在“自陷跃迁”。在简单的重整化有效带理论中，物理学可以完全理解为不同跳跃项之间的竞争。进一步的过渡的可能性建议的结果。
英文摘要：
Non-diagonal couplings to a bosonic bath completely change polaronic dynamics, from the usual diagonally-coupled paradigm of smoothly-varying properties. We study, using analytic and numerical methods, a model having both diagonal Holstein and non-diagonal Su-Schrieffer-Heeger (SSH) couplings. The critical coupling found previously in the pure SSH model, at which the $k=0$ effective mass diverges, now becomes a transition line in the coupling constant plane - the form of the line depends on the adiabaticity parameter. Detailed results are given for the quasiparticle and ground state properties, over a wide range of couplings and adiabaticity ratios. The new paradigm involves a destabilization, at the transition line, of the simple Holstein polaron to one with a finite ground-state momentum, but with everywhere a continuously evolving band shape. No 'self-trapping transition' exists in any of these models. The physics may be understood entirely in terms of competition between different hopping terms in a simple renormalized effective band theory. The possibility of further transitions is suggested by the results.
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