Correlations in van der Waals [Hetero]Structures by the Spectroscopic Fingerprints of Quasiparticles and Collective Excitations

我们的联合实验和理论研究项目侧重于范德华[异质]结构的相关效应，特别是它们的光谱指纹图谱。通过将微观强耦合和弱耦合理论与集体模式的共振非弹性光散射光谱相结合，我们旨在阐明以下基本问题：(i)电子-电子和电子-声子相互作用如何决定范德华异质结构中的涌现现象和有序？（ii）范德华异质结构与局部应变、无序性和非均质性的相关性有多强？（iii）通过探索范德华异质结构特有的新（光学）探针可以学到什么？对于最后一个问题，我们将确定并利用新的实验技术，包括集体电荷密度激发的光谱，这些技术可以提供关于这些系统中相关性本质的特别有价值的信息。为了解决这些问题，我们将研究各种系统，包括表现出相关绝缘状态和相关金属的TMDC异质结构（如M=Mo， W的MX2），具有moir<s:1>诱导超导状态的石墨烯（moir<s:1>）多层，以及涉及已经相关的组成材料（如Mott-Hubbard层和磁性层）的“新型”界面。在方法论上，我们的研究将采用互补的理论方法，特别是动态平均场理论和弱耦合展开（随机相位近似和泛函重整化群技术）。为了处理电子相关性，这些方法将应用于基于原子紧密结合和连续体描述的模型。此外，在必要的地方，将获得电子-声子耦合的从头计算估计。为了从实验方面连接这一点，将使用非弹性光散射和集体模式和声子的光谱学来探测相关效应。这一建议的研究将绘制出一幅更完整的范德华[异质]结构中涌现现象的图景，该图景由实验证实的理论定量预测所支持。

Our joint experimental and theoretical research project focuses on correlation effects in van der Waals [hetero]structures and in particular their spectroscopic fingerprints. By combining microscopic strong and weak coupling theories with resonant inelastic light scattering spectroscopy of collective modes, we aim to shed light on the following fundamental questions: (i) How does the interplay of electron-electron and electron-phonon interaction determine emergent phenomena and ordering in van der Waals heterostructures? (ii) How robust are correlations in van der Waals heterostructures with respect to local strain, disorder, and inhomogeneities? (iii) What can be learned by the exploration of new (optical) probes unique to van der Waals heterostructures for correlated phenomena? For the last question we will identify and utilize novel experimental techniques including spectroscopies on collective charge density excitations that can provide particularly valuable information on the nature of correlations in these systems. To address these questions, we will study various systems, including TMDC heterostructures (such as MX2 with M=Mo, W) exhibiting correlated insulating states and correlated metals, graphene (moiré) multilayers with moiré-induced superconducting states, as well as "novel" interfaces involving already correlated constituent materials like Mott-Hubbard layers and magnetic layers. Methodologically our research will employ complementary theoretical methods, particularly dynamical mean field theory and weak coupling expansions (random phase approximation and functional renormalization group techniques). In order to treat electron correlations, these methods will be applied to models based on atomistic tight-binding and continuum descriptions. Additionally, ab initio estimates of electron-phonon coupling will be obtained where necessary. To connect to this from the experimental side, inelastic light scattering and optical spectroscopy of collective modes and phonons will be used to probe correlation effects. The research of this proposal will draw a more complete picture of emergent phenomena in van der Waals [hetero]structures backed by quantitative predictions in theory corroborated by experiments.