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DF: Fachverband Dielektrische Festkörper

DF 20: Focus Session: Organic ferroelectrics

DF 20.3: Hauptvortrag

Donnerstag, 14. März 2013, 11:00–11:40, H11

Coupling of charge and spin order in organic charge transfer salts — •Martin Dressel — 1. Physikalisches Institut, Universität Stuttgart

Organic charge-transfer salts are renown for their conducting and even superconducting properties. But the metallic phase is not stable in reduced dimensions: at low temperatures the electronic charges and spins tend to arrange themselves in an orderly fashion due to relatively strong correlations. There is a growing number of molecular materials, such as TTF-CA, TMTTF, and BEDT-TTF salts, where electronic degrees of freedom and electronic interactions are directly responsible for electric polarization and ferroelectric transition, termed electronic ferroelectricity. This would enable wide applications for organic ferroelectrics in fast switching, sensor and data storage technology.

Recently, it was discovered that charge order not only produces ferroelectricity but also breaks the symmetry of the magnetic degree of freedom in organic quantum spin chains. An intense discussion takes place whether in two-dimensional organic compounds with a high degree of frustration ferroelectric order can induce magnetic order, leading to charge-order driven multiferroicity. There are even first hints for a spin-driven multiferroic state in compounds for which the on-site Coulomb repulsion is reduced making inter-site interaction more important.

No complete picture is possible at this point, nevertheless, we have the vision that the interplay of magnetic and electronic ferroicity paves the way towards organic spintronics.