Optical studies of $\kappa$-(ET)$_{2}$Cu[ N(CN)$_{2}$] Br$_{0.85}$Cl$_{0.15}$

J. Barz; M. Dumm; M. Dressel; C. Mézière; P. Batail

doi:doi:10.1051/jp4:2004114061

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


Page(s)		289 - 290
DOI		https://doi.org/10.1051/jp4:2004114061

J. Phys. IV France 114 (2004) 289
DOI: 10.1051/jp4:2004114061

Optical studies of $\kappa$ -(ET) ₂Cu[ N(CN) ₂] Br _0.85Cl _0.15

J. Barz¹, M. Dumm^{1, 1}, M. Dressel¹, C. Mézière² and P. Batail²

¹ Physikalisches Institut, Universität Stuttgart, Pfaffenwaldring 57, 70550 Stuttgart, Germany
² Laboratoire CIMI, FRE 2447 CNRS-Université d'Angers, Bât. K, UFR Sciences, 2 Bd. Lavoisier, 49045 Angers, France

Abstract
The low-temperature ground states of the quasi two-dimensional layered organic charge transfer salts $\kappa$ -(ET) ₂Cu[ N(CN) ₂] Br _1-xCl _x are known to be strongly dependent on the Br/Cl content of the anions. At low temperatures, pure Cl compounds undergo a phase transition into an antiferromagnetic ground state while the pure Br compound is a organic superconductor. Here we present polarized infrared reflectivity measurements on the compound with 85% bromine and 15% chlorine. Our measurements were performed within the highly conducting a-c plane. From room temperature down to 90 K, we observe the typical signatures of a semiconductor in our spectra. When the sample is cooled down further, a significant amount of spectral weight is shifted towards lower frequencies. At 6 K, a Drude-like optical conductivity is observed in the far infrared Key words. charge-transfer salts - organic superconductors - optical properties.

Optical studies of -(ET) 2Cu[ N(CN) 2] Br 0.85Cl 0.15

Optical studies of $\kappa$ -(ET) ₂Cu[ N(CN) ₂] Br _0.85Cl _0.15