Anisotropic charge dynamics in the quantum spin-liquid candidate κ−(BEDT-TTF)2Cu2(CN)3

Pinterić, Marija and Čulo, M. and Milat, Ognjen and Basletić, Mario and Korin-Hamzić, Bojana and Tafra, Emil and Hamzić, Amir and Ivek, T. and Peterseim, T. and Miyagawa, K. and Kanoda, K. and Schlueter, J. A. and Dressel, M. and Tomić, S. (2014) Anisotropic charge dynamics in the quantum spin-liquid candidate κ−(BEDT-TTF)2Cu2(CN)3. Physical Review B, 90 (19). pp. 195139-13. ISSN 1098-0121

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We have in detail characterized the anisotropic charge response of the dimer Mott insulator κ−(BEDT-TTF)2Cu2(CN)3 by dc conductivity, Hall effect, and dielectric spectroscopy. At room temperature, the Hall coefficient is positive and close to the value expected from stoichiometry; the temperature behavior follows the dc resistivity ρ(T). Within the planes the dc conductivity is well described by variable-range hopping in two dimensions; this model, however, fails for the out-of-plane direction. An unusually broad in-plane dielectric relaxation is detected below about 60 K; it slows down much faster than the dc conductivity following an Arrhenius law. At around 17 K, we can identify a pronounced dielectric anomaly concomitantly with anomalous features in the mean relaxation time and spectral broadening. The out-of-plane relaxation, on the other hand, shows a much weaker dielectric anomaly; it closely follows the temperature behavior of the respective dc resistivity. At lower temperatures, the dielectric constant becomes smaller both within and perpendicular to the planes; also, the relaxation levels off. The observed behavior bears features of relaxorlike ferroelectricity. Because heterogeneities impede its long-range development, only a weak-tunneling-like dynamics persists at low temperatures. We suggest that the random potential and domain structure gradually emerge due to the coupling to the anion network.

Item Type: Article
Date: November 2014
Subjects: NATURAL SCIENCES > Physics
Additional Information: Copyright (2014) by the American Physical Society.
Divisions: Faculty of Science > Department of Physics
Publisher: American Physical Society
Depositing User: Gordana Stubičan Ladešić
Date Deposited: 25 Nov 2014 12:04
Last Modified: 24 Nov 2017 14:06

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