论文标题
大型非谐双极的稳定条件
Stability conditions for a large anharmonic bipolaron
论文作者
论文摘要
大极颗子是一种准颗粒，由与材料的声子相互作用的几乎游离的电子组成，其晶格参数远小于极化尺度。电子 - 光子相互作用还导致电子之间的吸引人相互作用，这可以使两个极性子配对并形成双二或双极。已经表明，由于强大的1电子-1-phonon耦合，因此在理论上可以形成大型双极，但是在实际材料中没有看到它们，因为所需的电子 - phonon相互作用的临界值太大。在这里，我们研究了1-电子-2-phonon耦合对大双子龙问题的影响。 从FröhlichHamiltonian的概括开始，该汉密尔顿量包括标准的1-电子-1-Phonon相互作用以及Anharmonic 1-Electron-2-Phonon相互作用，我们使用路径积分方法来找到半分析的上层绑定的Bipolaron Energy bot the Bipolaron Energy to Bipolaron Energy均可在FröhlichCouplingCoupling Coupling Coupling $ al的所有值中有效。我们通过将双极能量与两个游离极性子的能量进行比较，发现双极相图和双丙酸酯稳定性的条件。 Fröhlich耦合强度$α_ {\ text {Crit}} $的临界值是根据1-电子-2-Phonon相互作用的强度的函数计算的。结果表明，在具有显着的1-电子-2-Phonon相互作用以及强大的1电子-1-Phonon相互作用（例如钛酸腹膜）的材料中，大型双极形成更有可能。
A large polaron is a quasiparticle that consists of a nearly free electron interacting with the phonons of a material, whose lattice parameters are much smaller than the polaron scale. The electron-phonon interaction also leads to an attractive interaction between electrons, which can allow two polarons to pair up and form a bipolaron. It has been shown that large bipolarons can form in theory due to strong 1-electron-1-phonon coupling, but they have not been seen in real materials because the critical value of the required electron-phonon interaction is too large. Here, we investigate the effect of 1-electron-2-phonon coupling on the large bipolaron problem. Starting from a generalization of the Fröhlich Hamiltonian that includes both the standard 1-electron-1-phonon interaction as well as an anharmonic 1-electron-2-phonon interaction, we use the path integral method to find a semi-analytical upper bound for the bipolaron energy that is valid at all values of the Fröhlich coupling strength $α$. We find the bipolaron phase diagram and conditions for the bipolaron stability by comparing the bipolaron energy to the energy of two free polarons. The critical value of the Fröhlich coupling strength $α_{\text{crit}}$ is calculated as a function of the strength of the 1-electron-2-phonon interaction. The results suggest that large bipolaron formation is more likely in materials with significant 1-electron-2-phonon interaction as well as strong 1-electron-1-phonon interaction, such as strontium titanate.
