Dresden 2006 – wissenschaftliches Programm
Bereiche | Tage | Auswahl | Suche | Downloads | Hilfe
DF: Dielektrische Festkörper
DF 9: Phase Transitions
DF 9.3: Vortrag
Donnerstag, 30. März 2006, 10:50–11:10, M{\"U}L Elch
Soliton Density in Incommensurate Thiourea — •Robert Blinc1 and Tomaž Apih2 — 1J. Stefan Institute, Jamova 39, Ljubljana, Slovenia — 2. Stefan Institute, Jamova 39, Ljubljana, Slovenia
Whereas soliton regimes have been reported in the past in type I incommensurate systems where the order parameter is at least two-dimensional and a Lifshitz invariant drives the system to a modulated incommensurate phase, this is not the case with type II incommensurate systems such as thiourea. Here there is no Lifshitz invariant and the order parameter is one-dimensional. It has been generally assumed until recently that the incommensurate modulation of type II systems is always of the plane wave type. Recent X-ray scattering results seem to show the appearance of soliton like modulation profiles close to the lock-in transition in thiourea. Perez - Mato provided a possible theoretical explanation of this situation. Here we show that the deuteron NMR spectra of thiourea exhibit a gradual change of the incommmensurate modulation wave from the plane wave to the soliton type. We determined the temperature dependence of the soliton density and compare the results with the theory of Perez - Mato. The obtained data support the above mentioned theoretical results and show that type II incommensurate systems can indeed exhibit a multi soliton lattice regime similar to that found in type I incommensurate systrems like RbZnCl4 and others.