Evolution of the charge carrier properties and electronic correlations in layered organic metals near the Mott metal-insulator transition

莫特相变是正常金属中最基本的关联驱动不稳定性之一。尽管有广泛的研究，但仍有重要的未解决的问题和开放的问题，特别是关于在明确定义的模型系统中绝缘态附近的金属基态的实验研究。在这个项目中，我们与来自实验和理论物理以及材料科学的专家一起解决这些问题。我们将使用Kappa类型的有机电荷转移盐作为准2D电子模型系统，具有带宽控制的Mott不稳定性，以跟踪相图中金属/绝缘体共存区域以及邻近的均匀金属态中载流子的关键特征的演变。特别是，我们将研究(I)关联诱导的有效质量的重整化，(Ii)费米表面的精确几何和拓扑，以及(Iii)电荷输运的相干性。在定义良好的模型系统中对这些特性的系统研究将为现有的Mott金属-绝缘体相变理论提供关键的检验。该项目的一个关键目标是解缠电荷、自旋和晶格自由度对金属-绝缘体不稳定性的贡献。这个问题将通过研究具有不同强度的几何受挫、磁相互作用和晶格无序的卡帕型盐来解决。具有不同阴离子的BEDT-TTF盐特别适合于研究几何受挫效应，而具有局域磁矩的BEDT-TTF盐则提供了电子关联和磁相互作用之间的相互作用。电子态与晶格自由度的耦合将通过研究BEDT-TTF盐中的氢化对载流子性质的影响以及追踪这些盐中乙烯基无序的影响来探索。解决上述问题的主要实验探针将是磁量子振荡、半经典各向异性磁输运和电阻率各向异性。通过微调材料的准静水压力和“化学压力”，可以实现对金属-绝缘体边界电子基态的精确控制。参与该项目的理论小组将利用准2D金属中的高场磁输运以及相分离电子介质中的电荷输运的最新理论，对实验结果进行定量分析。计划在与拟议的实验相关的部分进一步发展(磁)输运理论。高质量的卡帕型盐单晶的可用性对计划的项目的成功至关重要。这种晶体的制备和表征将由该项目经验丰富的材料科学小组进行。

The Mott transition is one of the most fundamental correlation-driven instabilities in normal metals. Despite extensive studies, there are important unresolved problems and open questions, in particular regarding the experimental study of the metallic ground state in the immediate vicinity of the insulating state in well-defined model systems. Within this project, we join experts from experimental and theoretical physics and materials science to tackle these problems. We will employ kappa-type organic charge transfer salts as quasi-2D electronic model systems with bandwidth-controlled Mott instability for tracking the evolution of key characteristics of the charge carriers in the metal/insulator coexistence region of the phase diagram as well as in the neighboring homogeneous metallic state. In particular, we will study (i) the correlation-induced renormalization of the effective mass, (ii) the exact geometry and topology of the Fermi surface, and (iii) the coherence of charge transport. The systematic study of these characteristics in well-defined model systems will provide a crucial test for the existing theories of the Mott metal-insulator transition.A key objective of the project is the disentanglement of contributions of charge, spin, and lattice degrees of freedom to the metal-insulator instability. This problem will be addressed by studying kappa-type salts with different strength of geometrical frustration, magnetic interactions, and lattice disorder. The salts of BEDT-TTF with different anions are particularly suited for studying the effects of geometrical frustration, while BETS salts with localized magnetic moments give access to the interplay between electronic correlations and magnetic interactions. The coupling of the electronic state to lattice degrees of freedom will be probed by studying the influence of deuteration of BEDT-TTF salts on the charge carrier properties and by tracing the impact of ethylene-group disorder in these salts.The main experimental probes for addressing the above issues will be magnetic quantum oscillations, semiclassical anisotropic magnetotransport, and resistivity anisotropy. A precise control of the electronic ground state with respect to the metal-insulator boundary will be realized by fine-tuning materials with quasi-hydrostatic pressure as well as "chemical pressure". A quantitative analysis of the experimental results will be carried out by the theory team involved in the project using the state-of-the-art theory of high-field magnetotransport in quasi-2D metals as well as of the charge transport in phase-separated electronic media. Further development of the (magneto)transport theory in the segments related to the proposed experiments is planned.The availability of top-quality single crystals of kappa-type salts is crucial for the success of the planned project. The preparation and characterization of such crystals will be carried out by the experienced materials science team of the project.