Experimental Studies of Organic Charge Transfer Salts

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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.