Day / Time
Date(s) - 01/04/2014
13 h 00 min - 15 h 00 min
Auditoire Stückelberg, 24 quai Ernest Ansermet
Alessandro Scarfato (group of Prof. Renner)
A chiral character of the CDW in 1T-TiSe2 has been inferred from optical and STM experiments. The chirality is currently understood in terms of the superposition of three 3D-CDWs. The relative phase shift between them yields an ordered change of orientation in the stacking direction of the layers. This helical state has been identified in the Fourier Bragg peaks of STM micrographs. Here we compare the CDW registry and contrast on adjacent terraces in STM micrographs acquired across step edges. These results are not compatible with the current 3D-CDWs model, leading us to propose an alternative scenario.
Krunoslav Prsa (group of Prof. Ruegg)
Atomic spin systems where magnetic interactions are frustrated by lattice geometry provide a fruitful source of emergent phenomena. The degeneracy inherent in frustrated systems may prevail all the way down to absolute zero temperature or it may be lifted by small perturbations or entropic effects. In the geometrically frustrated Ising magnet Ca3Co2O6 we follow the temporal and spatial evolution of nanoscale magnetic fluctuations firmly embedded inside the spin-density-wave magnetic structure. These fluctuations are a signature of a competing ferrimagnetic phase with an incommensurability that is different from, but determined by the host magnetic structure. As the temperature is lowered, the fluctuations slow down into a regime of stable spatiotemporal nanostructures.
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