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

M. Pinterić, M. Čulo, O. Milat, M. Basletić, B. Korin-Hamzić, E. Tafra, A. Hamzić, T. Ivek, T. Peterseim, K. Miyagawa, K. Kanoda, J. A. Schlueter, M. Dressel, and S. Tomić
Phys. Rev. B 90, 195139 – Published 20 November 2014

Abstract

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.

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  • Received 21 July 2014
  • Revised 10 October 2014

DOI:https://doi.org/10.1103/PhysRevB.90.195139

©2014 American Physical Society

Authors & Affiliations

M. Pinterić1,2, M. Čulo1, O. Milat1, M. Basletić3, B. Korin-Hamzić1, E. Tafra3, A. Hamzić3, T. Ivek1,4, T. Peterseim4, K. Miyagawa5, K. Kanoda5, J. A. Schlueter6, M. Dressel4, and S. Tomić1

  • 1Institut za fiziku, P.O. Box 304, HR-10001 Zagreb, Croatia
  • 2Faculty of Civil Engineering, Smetanova 17, 2000 Maribor, Slovenia
  • 3Department of Physics, Faculty of Science, University of Zagreb, P.O. Box 331, HR-10001 Zagreb, Croatia
  • 41. Physikalisches Institut, Universität Stuttgart, Pfaffenwaldring 57, D-70550 Stuttgart, Germany
  • 5Department of Applied Physics, University of Tokyo, Tokyo 113-8656, Japan
  • 6Material Science Division, Argonne National Laboratory, Argonne, Illinois 60439-4831, USA

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Issue

Vol. 90, Iss. 19 — 15 November 2014

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