Hirotada Hoshino

Electrical and Structural Properties of θ-type BEDT-TTF Organic Conductors under Uniaxial Strain

In order to investigate the relationships between crystal structures and electronic properties of θ-type BEDT-TTF organic conductors, electrical properties of θ-(BEDT-TTF) 2 Ag(CN) 2 and θ-(BEDT-TTF) 2 CsZn(SCN) 4 and crystal structures of θ-(BEDT-TTF) 2 CsZn(SCN) 4 under uniaxial strain are investigated. The resistivity measurements for both salts under uniaxial strain show that the inter-columnar uniaxial strain preserves the metallic nature while the intra-columnar one induces an insulating behavior, which are reminiscent of the charge-ordered state of θ-(BEDT-TTF) 2 RbZn(SCN) 4 . Structure analyses of θ-(BEDT-TTF) 2 CsZn(SCN) 4 under uniaxial strain indicate that the inter-columnar strain slightly increases the diagonal transfer integral but does not vary the vertical one, and the intra-columnar uniaxial strain largely increases the vertical transfer integral but does not change the diagonal one. Based on these experimental results, the key parameters to determine the electrical properties of θ-type B...

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

Abstract 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.

ESR Investigation of Organic Conductors (DTM-TTP)(TCNQ)(TCE) and (TMET-TTP) 2(TCNQ)

Magnetic properties of the title compounds are investigated by ESR measurements, and from the temperature dependence of the g -values, the spin susceptibility is separated into donor and TCNQ contr...

Uniaxial Strain Effect on the θ-Phase Organic Conductor with a Large Dihedral Angle, θ-(TMET-TTP)4PF6

For the organic conductor θ-(TMET-TTP) 4 PF 6 (TMET-TTP: 2-[4,5-bis(methylthio)-1,3-dithiol-2-ylidene]-5-(4,5-ethylenedithio-1,3-dithiol-2-ylidene)-1,3,4,6-tetrathiapentalene), electrical resistanc...

Control of electronic properties of organic superconductors by uniaxial strain method

We controlled the electronic properties of BEDT-TTF based organic conductors by using the uniaxial strain method. Electronic properties of θ-(BEDT-TTF) 2 CsZn(SCN) 4 were able to be controlled as suggested by the unified phase diagram proposed to this series of compounds. α-(BEDT-TTF) 2 XH g (SCN) 4 (X=K, NH 4 ) showed essentially the same properties if their lattice parameters are appropriately controlled by the uniaxial strain method. Furthermore the reduction of the lattice parameter c enhanced the superconductivity suggesting that conventional discussions based on the volume effect is insufficient.

Metallic 1:1-composition organic conductors and the estimated U and V

Properties of metallic TTM-TTP (2,5-bis[4,5-bis(methylthio)-1,3-dithiol-2-ylidene]-1,3,4,6-tetrathiapentalene) salts with 1:1 composition, in particular magnetic properties of (TTM-TTP)[C(CN) 3 ], are reported. The results are discussed on the basis of molecular orbital calculations of on-site and off-site Coulomb integrals, U and V.

Universal Phase Diagram of θ-Type TMET-TTP Salts

A new θ-type TMET-TTP (2-[4,5-bis(thiomethyl)-1,3-dithiol-2-ylidene]-5-(4,5- ethylenedithio-1,3-dithiol-2-ylidene)-1,3,4,6-tetrathiapentalene) salt (TMET-TTP) 2 HSO 4 , which has smaller dihedral angle (116°), and has 2:1 composition, is prepared. This salt undergoes a M-I transition at around 100 K. The ESR measurement indicates that the low-temperature insulating state of this complex is paramagnetic. Thanks to this exceptional salt, a universal phase diagram of θ-type TTP salts can be discussed similarly to θ-type ET salts. In the θ-type ET salts, the universal phase diagram holds in the uniform quarter-filled band. However, our works in the θ-type TMET-TTP salts prove that the universal phase diagram is not largely influenced by the band-filling and the position of E F .