Spectroscopic characterization of charge order fluctuations in BEDT-TTF metals and superconductors

• Published in: Physica Status Solidi. B: Basic Solid State Physics Vol. 249; no. 5; pp. 953 - 956
• Main Authors: Girlando, A., Masino, M., Kaiser, S., Sun, Y., Drichko, N., Dressel, M., Mori, H.
• Format: Journal Article
• Language: English
• Published: Berlin WILEY-VCH Verlag 01.05.2012; WILEY‐VCH Verlag
• Subjects: Band spectra; charge fluctuation model; charge order; Infrared; Infrared radiation; metal-insulator transition; organic superconductors; Oscillator strengths; Solid state physics; Spectra; Spectral signatures; Superconductivity
• ISSN: 0370-1972; 1521-3951
• DOI: 10.1002/pssb.201100722

The charge‐fluctuating and charge‐ordered states in metallic, insulating and superconducting bis(ethylenedithio)tetrathiafulvalene (BEDT‐TTF) salts are characterized through the analysis of the infrared (IR) spectral region relevant to the CC antisymmetric stretch, b1ν22. This spectral region shows dramatic changes in band intensity and band‐shape by varying the temperature. The observed spectral features can be understood on the basis of an extension of the well‐known Kubo model for the spectral signatures of an equilibrium between two states. The two‐orders of magnitude increase in the IR oscillator strength of the b1ν22 mode upon ionization has also to be taken into account. BEDT‐TTF CC antisymmetric stretch, b1ν22.