Infrared optical conductivity and the electronic phase diagram in the organic superconductor $\kappa $-(BEDT-TTF)$_{2}$X

I. Ito; T. Sasaki; N. Yoneyama; N. Kobayashi; N. Hanasaki; H. Tajima; T. Ito; Y. Iwasa

doi:doi:10.1051/jp4:2004114071

Numéro		J. Phys. IV France Volume 114, April 2004


Page(s)		321 - 322
DOI		https://doi.org/10.1051/jp4:2004114071

J. Phys. IV France 114 (2004) 321
DOI: 10.1051/jp4:2004114071

Infrared optical conductivity and the electronic phase diagram in the organic superconductor $\kappa$ -(BEDT-TTF) ₂X

I. Ito¹, T. Sasaki¹, N. Yoneyama¹, N. Kobayashi¹, N. Hanasaki², H. Tajima², T. Ito³ and Y. Iwasa¹

¹ Institute for Materials Research, Tohoku University, Sendai 980-8577, Japan
² Institute for Solid State Physics, University of Tokyo, Kashiwa 277-8581, Japan
³ JAIST Hokuriku, Ishikawa 277-8581, Japan

Abstract
The polarized optical reflectance spectra of $\kappa$ -(BEDT-TTF) ₂Cu(NCS) ₂ and its deuterated one are measured in the infrared region. Both the specific molecular vibration mode $\nu _{3}(a_{g})$ of the BEDT-TTF molecule and the optical conductivity hump in the mid-infrared region change correlatively at T*=45-50K. The results suggest that the electron-molecular vibration coupling on the $\nu _{3}(a_{g})$ mode becomes weak due to the enhancement of the itinerant nature of the carriers on the BEDT-TTF dimers below T*. The present observations demonstrate that two different metallic states are regarded as a correlated good metal below T* and a half filling bad metal above T*. Key words. $\kappa$ -(BEDT-TTF) ₂Cu(NCS) ₂, optical conductivity, electron-molecular vibration coupling.

Infrared optical conductivity and the electronic phase diagram in the organic superconductor -(BEDT-TTF) 2X

Infrared optical conductivity and the electronic phase diagram in the organic superconductor $\kappa$ -(BEDT-TTF) ₂X