We report comprehensive Raman and infrared investigations of charge-order (CO) fluctuations in the organic metal β''-(BEDT-TTF)2SF5CHFSO3 and superconductor β''-(BEDT-TTF)2SF5CH2CF2SO3. The charge-sensitive vibrational bands are analyzed through an extension of the well-known Kubo model for the spectral signatures of an equilibrium between two states. At room temperature, both salts exhibit charge fluctuations between two differently charged molecular states with an exchange frequency of about 6×1011s−1. The exchange rate of the metallic salt remains roughly constant down to 10 K, while in the superconductor, the exchange velocity starts to decrease below 200 K, and a “frozen” charge-ordered state emerges and coexists with the charge-order fluctuation state down to the superconducting temperature. These findings are confronted with other spectroscopic experiments, and a tentative phase diagram is proposed for the β'' BEDT-TTF quarter-filled salts.

Charge-order fluctuations and superconductivity in two-dimensional organic metals / Alberto Girlando; Matteo Masino; John A. Schlueter; Natalia Drichko; Stefan Kaiser; Martin Dressel. - In: PHYSICAL REVIEW. B, CONDENSED MATTER AND MATERIALS PHYSICS. - ISSN 1098-0121. - 89(2014), pp. 174503-1-174503-9. [10.1103/PhysRevB.89.174503]

Charge-order fluctuations and superconductivity in two-dimensional organic metals

GIRLANDO, Alberto;MASINO, Matteo;
2014

Abstract

We report comprehensive Raman and infrared investigations of charge-order (CO) fluctuations in the organic metal β''-(BEDT-TTF)2SF5CHFSO3 and superconductor β''-(BEDT-TTF)2SF5CH2CF2SO3. The charge-sensitive vibrational bands are analyzed through an extension of the well-known Kubo model for the spectral signatures of an equilibrium between two states. At room temperature, both salts exhibit charge fluctuations between two differently charged molecular states with an exchange frequency of about 6×1011s−1. The exchange rate of the metallic salt remains roughly constant down to 10 K, while in the superconductor, the exchange velocity starts to decrease below 200 K, and a “frozen” charge-ordered state emerges and coexists with the charge-order fluctuation state down to the superconducting temperature. These findings are confronted with other spectroscopic experiments, and a tentative phase diagram is proposed for the β'' BEDT-TTF quarter-filled salts.
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Utilizza questo identificativo per citare o creare un link a questo documento: http://hdl.handle.net/11381/2711695
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