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- ItemB-T phase diagram of Pd/Fe/Ir(111) computed with parallel tempering Monte Carlo([Bad Honnef] : Dt. Physikalische Ges., 2018) Böttcher, M.; Heinze, S.; Egorov, S.; Sinova, J.; Dupé, B.We use an atomistic spin model derived from density functional theory calculations for the ultra-thin film Pd/Fe/Ir(111) to show that temperature induces coexisting non-zero skyrmion and antiskyrmion densities. We apply the parallel tempering Monte Carlo method in order to reliably compute thermodynamical quantities and the B–T phase diagram in the presence of frustrated exchange interactions. We evaluate the critical temperatures using the topological susceptibility. We show that the critical temperatures depend on the magnetic field in contrast to previous work. In total, we identify five phases: spin spiral, skyrmion lattice, ferromagnetic phase, intermediate region with finite topological charge and paramagnetic phase. To explore the effect of frustrated exchange interactions, we calculate the B–T phase diagram, when only effective exchange parameters are taken into account.
- ItemDiscontinuous switching of position of two coexisting phases([Bad Honnef] : Dt. Physikalische Ges., 2018) Krüger, Samuel; Weber, Christoph A.; Sommer, Jens-Uwe; Jülicher, FrankLiquid–liquid phase separation leads to the formation of condensed phases that coexist with a fluid. Here we investigate how the positions of a condensed phase can be controlled by using concentration gradients of a regulator that influences phase separation. We consider a mean field model of a ternary mixture where a concentration gradient of a regulator is imposed by an external potential. A novel first order phase transition occurs at which the position of the condensed phase switches in a discontinuous manner. This mechanism could have implications for the spatial organisation of biological cells and provides a control mechanism for droplets in microfluidic systems.