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arXiv · 1711.07384

Evidence for electronically-driven ferroelectricity in the family of strongly correlated dimerized BEDT-TTF molecular conductors

Elena Gati·Jonas K. H. Fischer·Peter Lunkenheimer·David Zielke·Sebastian Köhler·Felizitas Kolb·Hans-Albrecht Krug von Nidda·Stephen M. Winter·Harald Schubert·John A. Schlueter·Harald O. Jeschke·Roser Valenti·Michael Lang
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Abstract

By applying measurements of the dielectric constants and relative length changes to the dimerized molecular conductor $\kappa$-(BEDT-TTF)$_2$Hg(SCN)$_2$Cl, we provide evidence for order-disorder type electronic ferroelectricity which is driven by charge order within the (BEDT-TTF)$_2$ dimers and stabilized by a coupling to the anions. According to our density functional theory calculations, this material is characterized by a moderate strength of dimerization. This system thus bridges the gap between strongly dimerized materials, often approximated as dimer-Mott systems at 1/2 filling, and non- or weakly dimerized systems at 1/4 filling exhibiting charge order. Our results indicate that intra-dimer charge degrees of freedom are of particular importance in correlated $\kappa$-(BEDT-TTF)$_2$X salts and can create novel states, such as electronically-driven multiferroicity or charge-order-induced quasi-1D spin liquids.

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Elena Gati, Jonas K. H. Fischer, Peter Lunkenheimer, David Zielke, Sebastian Köhler, Felizitas Kolb, Hans-Albrecht Krug von Nidda, Stephen M. Winter, Harald Schubert, John A. Schlueter, Harald O. Jeschke, Roser Valenti, Michael Lang. 2017-11-20. Evidence for electronically-driven ferroelectricity in the family of strongly correlated dimerized BEDT-TTF molecular conductors. https://doi.org/10.1103/physrevlett.120.247601

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