Experimental Studies of Organic Charge Transfer Salts

这项研究的目标是探索低维、强相互作用和来自应用领域的挫折感如何共同作用，产生有趣的物质状态。其中一种材料(贝克加德盐)随着温度、压力和磁场的变化，呈现出金属、绝缘、反铁磁、密度波、超导、非欧姆、准周期和量子霍尔效应相。对准一维和准二维有机电荷转移盐的正常相、超导相和奇异相进行了磁测量、热测量、弹性测量和结构测量。没有在其他材料中发现的新现象也得到了检验。其中包括磁场诱导的级联跃迁和新形式的量子振荡。此外，还研究了高达65特斯拉的超强磁场对低维系统行为的影响。%在这项工作中，研究了高各向异性有机导体的电子性质。通常情况下，沿晶体最佳导电方向的导电性比沿最差导电方向的导电性好一百万倍。由于电子被限制沿链移动，它们与其他电子的相互作用更强，从而导致了一些不寻常的跃迁和性质。在室温下，这些材料是金属的。当冷却到液氦温度时，材料变成绝缘的、磁性的或超导的。当施加磁场并使其朝向与链不同的方向时，材料性质会发生显著变化。这些研究的目的是了解分子系统中金属与绝缘体、磁体和超导体之间的基本竞争。拟议研究的成功完成最终将导致新材料的开发，用于制造新的电子器件。

The goal of this research is to explore how low dimensions, strong interactions and frustration from applied fields act together to produce interesting states of matter. One such material (Bechgaard salt) exhibits metallic, insulating, antiferromagnetic, density wave, superconducting, non-ohmic, quasi-periodic and Quantum Hall Effect phases as temperature, pressure and magnetic field are varied. Experiments involving magnetic, thermal, elastic, and structural measurements are conducted on normal, superconducting and exotic phases of the quasi-one and quasi-two dimensional organic charge transfer salts. New phenomena found in no other materials also are examined. These include a cascade of magnetic field induced transitions and new forms of quantum oscillations. In addition, the effects of extraordinary magnetic field, up to 65 Tesla, on the behavior of low-dimensional systems are investigated. %%% In this work, electronic properties of highly anisotropic organic conductors are studied. Typically, the conductivity is one million times better along the best conducting direction of the crystal than along the worst. Because the electrons are constrained to move along chains, they interact more strongly with other electrons, thus causing a number of unusual transitions and properties. At room temperature, the materials are metallic. On cooling to liquid helium temperatures, the materials become insulating, magnetic or superconducting. When magnetic fields are applied and oriented in different directions relative to the chains, striking changes in material properties are noted. The object of these studies is to understand the basic competition between metals and insulator, magnet and superconductor in a molecular system. The successful completion of the proposed studies ultimately will lead to the development of new materials for fabrication of new electronic devices.