论文标题
具有二次电子相互作用的极化子
Polaron with Quadratic Electron-phonon Interaction
论文作者
论文摘要
我们使用两种替代方法学发展介绍了具有二次耦合到振荡器位移的二极化子的第一个数值精确研究。我们的结果涵盖了反绝热和绝热制度以及从系统的稳定性阈值$ g_2 = -1 $从$ g_2 \ gg gg 1 $中的任意强烈排斥，从系统的稳定性阈值$ g_2 $。二极管的关键特性证明，与线性对应物的关键特性截然不同。他们（i）甚至对大二次耦合也不敏感，除了在吸引人时不稳定性阈值附近的防绝热极限。 （ii）仅取决于绝热比率，但对电子分散和空间尺寸不敏感； （iii）即使在不稳定性点也具有弱晶格变形。我们的结果与极性材料低密度的电子的性质具有直接相关性，包括有关其超导状态的最新建议。
We present the first numerically exact study of a polaron with quadratic coupling to the oscillator displacement, using two alternative methodological developments. Our results cover both anti-adiabatic and adiabatic regimes and the entire range of electron-phonon coupling $g_2$, from the system's stability threshold at attractive $g_2=-1$ to arbitrary strong repulsion at $g_2 \gg 1$. Key properties of quadratic polarons prove dramatically different from their linear counterparts. They (i) are insensitive even to large quadratic coupling except in the anti-adiabatic limit near the threshold of instability at attraction; (ii) depend only on the adiabatic ratio but are insensitive to the electron dispersion and dimension of space; (iii) feature weak lattice deformations even at the instability point. Our results are of direct relevance to properties of electrons at low densities in polar materials, including recent proposals for their superconducting states.
