Semimetallic and charge-ordered $\alpha$-(BEDT-TTF)${}_2$I${}_3$: on the role of disorder in dc transport and dielectric properties

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.

10 pages, 7 figures, submitted to Physical Review B

References in corpus (8)

• Titanic Magnetoresistance in WTe2
• Charge Ordering in alpha-(BEDT-TTF)2I3 by synchrotron x-ray diffraction
• Effects of the Zero-Mode Landau Level on Inter-Layer Magnetoresistance in Multilayer Massless Dirac Fermion Systems
• Anisotropic charge dynamics in the quantum spin-liquid candidate $\kappa$-(BEDT-TTF)${}_2$Cu${}_2$(CN)${}_3$
• Pressure-dependent optical investigations of $\alpha$-(BEDT-TTF)${}_2$I${}_3$: tuning charge order and narrow gap towards a Dirac semimetal
• Anions effects on the electronic structure and electrodynamic properties of the Mott insulator $\kappa$-(BEDT-TTF)${}_2$Ag${}_2$(CN)${}_3$
• Electrically-induced phase transition in $\alpha$-(BEDT-TTF)${}_2$I${}_3$: Indications for high-mobility hot charge carriers
• Scattering dominated high-temperature phase of 1T-TiSe2: an optical conductivity study

Cited by in corpus (7)

• Molecular Quantum Materials: Electronic Phases and Charge Dynamics in Two-Dimensional Organic Solids
• Domain Wall Conductivity with strong Coulomb interaction of two-dimensional massive Dirac Electrons in the Organic Conductor $\alpha$-(BEDT-TTF)${}_2$I${}_3$
• Anomalous scaling law for thermoelectric transport of 2D-confined electrons in an organic molecular system
• Charge glass in an extended dimer Hubbard model
• Thermoelectric transport properties of the quasi-one-dimensional dimer-Mott insulator ${\beta }^{\prime }$-(BEDT-TTF)${}_2$ICl${}_2$
• Third-order Electrical Conductivity of the Charge-ordered Organic Salt $\alpha$-(BEDT-TTF)${}_2$I${}_3$
• Role of hydrogen bonding in charge-ordered organic conductor $\alpha$-(BEDT-TTF)${}_2$I${}_3$ probed by ${}^{127}$I nuclear quadrupole resonance