论文标题
从头开始计算自定位极性的规范转换和能量功能形式主义的比较
Comparison of the canonical transformation and energy functional formalisms for ab initio calculations of self-localized polarons
论文作者
论文摘要
在具有较强电子波（E-PH）相互作用的材料中，荷载体可以扭曲周围的晶格并被捕获，形成自定位的（小）极性。我们最近基于规范变换开发了一种从头算方法，以有效计算小极性子的形成和能量[1]。在最近的文献中提出了一种基于Landau-Pekar能量功能的不同方法[2,3]。在这项工作中，我们详细分析和比较了这两种方法。我们表明，使用相同的极性波函数时，小极极能量在两个形式主义中是相同的。我们还表明，我们的规范转化形式主义可以预测极化子带结构，并可以正确处理零和有限的温度晶格振动效应，尽管目前使用固定的极性波函数。相反，能量功能方法可以计算北极星波函数，但是当我们在这里显示时，它忽略了晶格振动，无法解决极化子自定位和热谱带狭窄。综上所述，这项工作涉及最近开发的两种不同的方法来研究第一原理的极性，强调了它们的优点和缺点，并在统一的形式主义中讨论了它们。
In materials with strong electron-phonon (e-ph) interactions, charge carriers can distort the surrounding lattice and become trapped, forming self-localized (small) polarons. We recently developed an ab initio approach based on canonical transformations to efficiently compute the formation and energetics of small polarons[1]. A different approach based on a Landau-Pekar energy functional has been proposed in the recent literature [2,3]. In this work, we analyze and compare these two methods in detail. We show that the small polaron energy is identical in the two formalisms when using the same polaron wave function. We also show that our canonical transformation formalism can predict polaron band structures and can properly treat zero- and finite-temperature lattice vibration effects, although at present using a fixed polaron wave function. Conversely, the energy functional approach can compute the polaron wave function, but as we show here it neglects lattice vibrations and cannot address polaron self-localization and thermal band narrowing. Taken together, this work relates two different methods developed recently to study polarons from first-principles, highlighting their merits and shortcomings and discussing them both in a unified formalism.
