Dresden 2006 – wissenschaftliches Programm
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TT: Tiefe Temperaturen
TT 25: Correlated Electrons - Poster Session
TT 25.3: Poster
Mittwoch, 29. März 2006, 14:30–18:30, P1
Charge order fluctuations in 1/4- filled conductors α-(BEDT-TTF)2MHg(SCN)4 (M=NH4,K,Tl,Rb) investigated by infrared spectroscopy. — •Natalia Drichko1, Martin Dressel1, Jaime Merino2, and Andres Greco3 — 11. Physikalisches Institut Universität Stuttgart, Germany — 2UAM, Spain — 3UNR-CONICET, Argentina
Electron-electron interactions determine the properties of the two-dimensional organic conductors α-(BEDT-TTF)2MHg(SCN)4 in a wide temperature range and can be tuned by variation of the charge reservoir layer: M=NH4, K, Tl, Rb. We study electronic properties of these compounds by infrared reflectance spectroscopy and compare our results with calculations performed for strongly correlated 1/4-filled conductors close to charge order transition. The observed Drude-like peak has only 10 % of the total spectral weight; we assign the shift of the spectral weight to higher frequencies to the fluctuations of charge order. For NH4 compound, influence of electronic correlations decrease with temperature. For the stronger correlated K and Tl salts, spectral indications of the short-range charge order at low temperatures are observed. The charge-carriers scattering rate exhibits the temperature dependence as predicted for fluctuating charge order. We suggest a generic phase diagram for α-(BEDT-TTF)2MHg(SCN)4 compounds depending on the strength of the electronic correlations. We further discuss its relevance to the superconducting ground state observed in NH4 material below 1 K and the density-wave ground state, observed below 10 K for the other members of this family.