Regensburg 2013 – wissenschaftliches Programm
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DF: Fachverband Dielektrische Festkörper
DF 20: Focus Session: Organic ferroelectrics
DF 20.4: Hauptvortrag
Donnerstag, 14. März 2013, 11:40–12:20, H11
Electrodynamics and ferroelectricity in two-dimensional molecular solids — •Silvia Tomic1, Tomislav Ivek1,2, Marko Pinteric1,3, Matija Culo1, Bojana Korin-Hamzic1, and Martin Dressel2 — 1Institut za fiziku, Zagreb, Croatia — 21.Physikalisches Institut, Universität Stuttgart, Germany — 3Fakulteta za gradbeništvo, Univerza v Mariboru, Slovenia
A variety of organics with reduced dimensionality and competing interactions between charges, spins and lattice display a multiplicity of ordering phenomena and complex phase diagrams. Novel forms of the low-temperature phases featuring ferroelectricity in the two-dimensional molecular solids have been in the focus of intense activity in recent years. Open issues concern the nature of collective charge excitations in the charge- and spin-order-driven ferroelectric phases as well as their coupling to applied dc and ac fields. And while some of their features resemble the well-established electrodynamics of conventional charge-density waves in 1D, I will demonstrate that others appear quite different and have not been encountered until now. In the charge-ordered phase with the formation of ferroelectric domains below the metal-to-insulator phase transition, the charge response seems to be reasonably well understood within a recent theoretical model. Conversely, rather intriguing is the dielectric response in Mott insulator phases with either canted antiferromagnetism or spin liquid. The result that neither charge disproportionation nor charge fluctuations could be detected by standard experimental techniques leaves the issue of spin-charge coupling fully open.