Microwave Conductivity in the Pure and Iodine‐Doped Organic Conductor α‐(BEDT‐TTF)₂I₃

Abstract

The microwave conductivity in dependence of temperature was measured on pure aod iodine doped crystals or a..(BEDT.1TFht) along the stack direction [100] and perpendicular to it [010]. The: uposure times 10 iodine were varied in many step!! between 2 mio and 360 min. The coouctless microwave technique enables to keep tbe same crystal in each case throughout all measurements. -The results show that the microwave conductivity vs. lemperalUre is not influenced distinctly by iodine doping. Only at the onset or the plateau range immediately below the metal·insolator transition at 135 K a small enhancement of the conductivity is round for exposure times larger than 60 min. -In 00 case a transition to a lIupercooductiog state is observed. Thererore recently reported superconductivity may be due to surface effects.

Field and frequency dependent transport in the two-dimensional organic conductor α-(BEDT-TTF)2I3

“…Between 10 GHz and 100 GHz the conductivity at 60 K increases almost two orders of magnitude. Qualitatively similar results were obtained for E II a and E II b in confirmation of reported results [3,10,21,23]. …”

Far infrared response of α- and αt-(BEDT-TTF)2I3

“…The phase-transition at TMI = 135 K in a-(ET)2I3 was studied by many different techniques [2,[5][6][7][8][9][10]. The crystal structure of a-(ET)2I3 contains sheets of ET molecules in the a-b plane separated by layers of 13 anions in the c-direction.…”

The infrared optical properties of the α-phase organic superconductor, α-(BEDT - TTF)2 (NH4Hg(NCS)4)

“…Various efforts to observe ambient pressure superconductivity in an a-phase BEDT-TTF salt like a-(BEDT-TTFhI 3 or related components a-(BEDT-TTFhAuI2 have failed: Doping of a-(BE-DT-TTFhI 3 ·with iodine does not cause a partial supression of the metal-insulator transition at 135 K and superconducting behaviour at T ~ 3 K as reported [2], but only gives a slight rise of the high-frequency conductivity in the insulating phase after extreme doping of several hours [3].…”