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arXiv · 1703.06055

Semimetallic and charge-ordered $\alpha$-(BEDT-TTF)$_2$I$_3$: 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·Bojana Korin-Hamzić
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Abstract

$\alpha$-(BEDT-TTF)$_2$I$_3$ 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 inter-pocket 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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Tomislav Ivek, Matija Čulo, Marko Kuveždić, Eduard Tutiš, Mario Basletić, Branimir Mihaljević, Emil Tafra, Silvia Tomić, Anja Löhle, Martin Dressel, Dieter Schweitzer, Bojana Korin-Hamzić. 2017-03-17. Semimetallic and charge-ordered $\alpha$-(BEDT-TTF)$_2$I$_3$: on the role of disorder in dc transport and dielectric properties. https://doi.org/10.1103/physrevb.96.075141

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