Semimetallic and charge-ordered α(BEDT-TTF)2I3: On the role of disorder in dc transport and dielectric properties

Tomislav Ivek, Matija Čulo, Marko Kuveždić, Eduard Tutiš, Mario Basletić, Branimir Mihaljević, Emil Tafra, Silvia Tomić, Anja Löhle, Martin Dressel, Dieter Schweitzer, and Bojana Korin-Hamzić
Phys. Rev. B 96, 075141 – Published 21 August 2017

Abstract

α(BEDT-TTF)2I3 is a prominent example of charge ordering among organic conductors. In this work, we explore the details of transport within the charge-ordered as well as semimetallic phase at ambient pressure. In the high-temperature semimetallic phase, the mobilities and concentrations of both electrons and holes conspire in such a way to create an almost temperature-independent conductivity as well as a low Hall effect. We explain these phenomena as a consequence of a predominantly interpocket scattering which equalizes mobilities of the two types of charge carriers. At low temperatures, within the insulating charge-ordered phase two channels of conduction can be discerned: a temperature-dependent activation, which follows the mean-field behavior, and a nearest-neighbor-hopping contribution. Together with negative magnetoresistance, the latter relies on the presence of disorder. The charge-ordered phase also features a prominent dielectric peak which bears a similarity to relaxor ferroelectrics. Its dispersion is determined by free-electron screening and pushed by disorder well below the transition temperature. The source of this disorder can be found in the anion layers which randomly perturb BEDT-TTF molecules through hydrogen bonds.

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  • Received 8 March 2017
  • Revised 11 July 2017

DOI:https://doi.org/10.1103/PhysRevB.96.075141

©2017 American Physical Society

Physics Subject Headings (PhySH)

Condensed Matter, Materials & Applied Physics

Authors & Affiliations

Tomislav Ivek1, Matija Čulo1,*, Marko Kuveždić1,2, Eduard Tutiš1, Mario Basletić2, Branimir Mihaljević2, Emil Tafra2, Silvia Tomić1, Anja Löhle3, Martin Dressel3, Dieter Schweitzer3, and Bojana Korin-Hamzić1

  • 1Institut za fiziku, P. O. Box 304, HR-10001 Zagreb, Croatia
  • 2Department of Physics, Faculty of Science, University of Zagreb, Bijenička cesta 32, 10000 Zagreb, Croatia
  • 3Physikalisches Institut, Universität Stuttgart, Pfaffenwaldring 57, D-70550 Stuttgart, Germany

  • *mculo@ifs.hr

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Vol. 96, Iss. 7 — 15 August 2017

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