Regensburg 2013 – wissenschaftliches Programm
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TT: Fachverband Tiefe Temperaturen
TT 55: Correlated Electrons: Low-Dimensional Systems -Materials 2
TT 55.1: Vortrag
Donnerstag, 14. März 2013, 09:30–09:45, H21
Absence of charge order in the dimerized κ-phase BEDT-TTF salts — •Martin Dressel1, Katrin Sedlmeier1, Sebastian Elsässer1, David Neubauer1, Rebecca Beyer1, Dan Wu1, Tomislav Ivek1,2, Silvia Tomic2, and John A. Schlueter3 — 11. Physikalisches Institut, Universität Stuttgart, Germany — 2Institut za fiziku, Zagreb, Croatia — 3Material Science Division, Argonne National Laboratory, U.S.A.
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
κ-(BEDT-TTF)2Cu2(CN)3, the
antiferromagnetic Mott insulator
κ-(BEDT-TTF)2Cu[N(CN)2]Cl, and the
superconductor κ-(BEDT-TTF)2Cu[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 ± 0.005 e. 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 κ-(BEDT-TTF)2Cu2(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.
[1] K. Sedlmeier et al., Phys. Rev. B (in press);
arXiv:1208.2652