论文标题
开发$ ab〜Initio $方法用于激子冷凝及其应用于$ \ bf tise_2 $
Development of $ab ~initio$ method for exciton condensation and its application to $\bf TiSe_2$
论文作者
论文摘要
激子凝结表明电子孔对自发形成会导致通过在费米表面的间隙开口通过间隙开口，从而导致从半学到激子绝缘子的相变。虽然已经提出了这种激子绝缘子的想法数十年，但是当前的理论方法只能提供定性描述，并且仍然缺少定量预测工具。为了洞悉此问题，我们基于有限温度的功能理论和多体扰动理论开发了一种$ ab〜iition $方法，以计算激子凝结临界行为。将我们的方法应用于单层$ \ rm tise_2 $，我们发现晶格失真并伴随着通过电子音纸耦合形成激子间隙而无需声音软化，证明了激子凝结是在这种化合物中观察到的电荷密度波的起源。总体而言，这项工作中引入的方法是一般的，并为寻找天然材料系统中的候选激素绝缘子铺平了道路。
Exciton condensation indicating the spontaneous formation of electron-hole pair can cause the phase transition from a semimetal to an excitonic insulator by gap opening at the Fermi surface. While the idea of this excitonic insulator has been proposed for decades, current theoretical approaches can only provide qualitative descriptions, and a quantitative predicting tool is still missing. To shed insight on this problem, we developed an $ab~initio$ method based on the finite-temperature density functional theory and many-body perturbation theory to compute the exciton condensation critical behavior. Applying our approach to the monolayer $\rm TiSe_2$, we find a lattice distortion accompanied by the formation of the excitonic gap via electron-phonon coupling without phonon softening, proving that the exciton condensation is the origin of the charge-density-wave state observed in this compound. Overall, the methodology introduced in this work is general and paves the way to searching for candidate excitonic insulators in natural material systems.
