Ordering phenomena in dimerized Mott insulators on a triangular lattice: effects of electronic correlations and anion coupling

三角晶格上二聚莫特绝缘体的有序现象：电子关联和阴离子耦合的影响

• 批准号: 286791755
• 负责人: Professor Dr. Martin Dressel
• 金额: --
• 依托单位: Zagreb Institute of Physics
• 依托单位国家: 德国
• 项目类别: Research Grants
• 财政年份: 2016
• 资助国家: 德国
• 起止时间: 2015-12-31 至 2021-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/286791755?language=en
• 关键词: Ordering; phenomena; dimerized; Mott; insulators

This project aims at the understanding of ordering phenomena in dimerized Mott insulators arranged on a triangular lattice, in particular the effect of electronic interactions and coupling to the anions. While the charge transfer salt kappa-(BEDT-TTF)2Cu2(CN)3 has been established as a reference system and prime candidate for spin liquid behavior, we choose two novel families of kappa-phase BEDT-TTF compounds for a comparative study in order to vary important parameters.1. In the first case of the Hg-family, the relative correlations are significantly varied: the dimers are arranged on a triangular lattice close to frustration but exhibit charge order at low temperatures, implying the importance of inter-site Coulomb repulsion. 2. For the Ag-analogue, the structure of the anion network and its coupling to the BEDT-TTF layer is different compared to kappa-(BEDT-TTF)2Cu2(CN)3. This will allow us to test the hypo¬thesis that frustration and intrinsic disorder of the anion layers affects the charge dynamics within the BEDT-TTF layers. By chemical substitution and physical pressure, we can fine-tune the relevant interactions and monitor how the physical properties are affected. In particular we investigate (i) the metal-insulator transition by transport measurements, (ii) the charge disproprtionation on the dimers by vibrational spectroscopy, (iii) the charge excitations by optical spectroscopy, and (iv) the relaxational behavior by dielectric spectro¬scopy. (v) Accompanying studies probe the susceptibility by SQUID and torque measurements and the magnetic behavior by ESR spectroscopy. (vi) We complement our experiments by numerical work on the electronic and phonon properties. We hope to clarify the collective charge excitations and the presence of spin-charge coupling in kappa--phase com¬pounds. This way we clarify the possibility of electronic multiferroicity in organic compounds and the possi¬bi¬lity of future applications.

该项目旨在了解排列在三角形晶格上的二聚Mott绝缘体中的有序现象，特别是电子相互作用和与阴离子耦合的影响。虽然电荷转移盐kappa-（BEDT-TTF）2Cu 2（CN）3已被确立为自旋液体行为的参考系统和主要候选者，但我们选择了两个新的κ相BEDT-TTF化合物家族进行比较研究，以改变重要参数。在第一种情况下的Hg-家庭，相对的相关性显着变化：二聚体排列在一个三角形晶格接近挫折，但在低温下表现出电荷顺序，这意味着网站间库仑排斥的重要性。2.对于Ag类似物，阴离子网络的结构及其与BEDT-TTF层的偶联与kappa-（BEDT-TTF）2Cu 2（CN）3不同。这将允许我们测试阴离子层的挫折和内在无序影响BEDT-TTF层内的电荷动力学的假设。通过化学取代和物理压力，我们可以微调相关的相互作用，并监测物理性质如何受到影响。特别地，我们研究（i）通过输运测量的金属-绝缘体转变，（ii）通过振动光谱的二聚体上的电荷disproprtionation，（iii）通过光谱的电荷激发，和（iv）通过介电光谱的弛豫行为。(v)伴随的研究通过SQUID和扭矩测量探测磁化率，并通过ESR光谱探测磁性行为。(vi)我们补充我们的实验的电子和声子性质的数值工作。我们希望澄清集体电荷激发和kappa相化合物中自旋-电荷耦合的存在。通过这种方式，我们阐明了有机化合物中电子多铁性的可能性和未来应用的可能性。