In-plane ESR microwave conductivity measurements and electronic band structure studies of the organic superconductor beta ''-(BEDT-TTF)(2)SF5CH2CF2SO3

The electronic structure of the organic superconductor beta "-(BEDT-TTF)(2) SF5CH2CF2SO3 (BEDT-TTF is bis(ethylenedithio)tetrathiafulvalene) was charac terized with the use of electron spin resonance (ESR) spectroscopy and elec tronic band structure calculations. The room-temperature ESR line width is 24-27 G in the plane of a donor molecule layer (i.e., in the ab-plane) and similar to 32 G along the normal to this plane (i.e., along the c*-directio n). The ab-plane anisotropy of the microwave conductivity was extracted for the first time from the ESR Dysonian line shape analysis. The in-plane con ductivity varies sinusoidally, is maximal along the interstack direction (b -axis), and is minimal along the donor stack direction (a-axis). The Fermi surfaces of the title compound consist of a 2D hole pocket and a pair of 1D wavy lines. The directions for the in-plane conductivity maximum and minim um are in excellent agreement with the electronic band structure calculated for beta "-(BEDT-TTF)(2)SF5CH2CF2SO3, and the origin of the in-plane condu ctivity anisotropy lies in the one-dimensional part of the Fermi surface. T his is the first time that an organic conductor shows Dysonian ESR line sha pe due to its 2D and strongly metallic nature, yet the 1D character is reve aled simultaneously through the in-plane conductivity anisotropy.