Structural control of organic conductors by uniaxial strain: θ- and α-phases of BEDT-TTF compounds

The crystalline and electronic structures of the α-phase BEDT-TTF organic superconductors were controlled by the uniaxial compression along the selected crystalline axes. We found the bandwidth to be increased by the compression parallel to the a-axis while the c-axis compression reduced the bandwidth. Similar controls were possible also in the θ-phase compounds. The a-axis compression made the material metallic although the c-axis one insulating. It is possible to systematically explain these changes in electronic properties under the uniaxial compression in terms of the changes in the electronic band structure in the conducting layer.