Absence of charge order in the dimerized kappa-phase BEDT-TTF salts

作者：Sedlmeier Katrin^*; Elsaesser Sebastian; Neubauer David; Beyer Rebecca; Wu Dan; Ivek Tomislav; Tomic Silvia; Schlueter John A; Dressel Martin

来源：Physical Review B, 2012, 86(24): 245103.

DOI：10.1103/PhysRevB.86.245103

Utilizing infrared vibrational spectroscopy we have investigated dimerized two-dimensional organic salts in order to search for possible charge redistribution that might constitute electronic dipoles and ferroelectricity: the quantum spin liquid kappa-(BEDT-TTF)(2)Cu-2(CN)(3) [BEDT-TTF: bis-(ethylenedithio)tetrathiafulvalene], the antiferromagnetic Mott insulator kappa-(BEDT-TTF)(2)Cu[N(CN)(2)]Cl, and the superconductor kappa-(BEDT-TTF)(2)Cu[N(CN)(2)]Br. None of them exhibit any indication of charge disproportionation. Upon cooling to low temperatures all BEDT-TTF molecules remain homogeneously charged within +/- 0.005e. No modification in the charge distribution is observed around T = 6 K where a low-temperature anomaly has been reported for the spin-liquid material kappa-(BEDT-TTF)(2)Cu-2(CN)(3). In this compound the in-plane optical response and vibrational coupling are rather anisotropic, indicating that the tilt of the BEDT-TTF molecules in c direction and their coupling to the anion layers has to be considered in the explanation of the electromagnetic properties.

• 出版日期2012-12-6