Negative phase time for Scattering at Quantum Wells: A Microwave Analogy Experiment

If a quantum mechanical particle is scattered by a potential well, the wave function of the particle can propagate with negative phase time. Due to the analogy of the Schr\"odinger and the Helmholtz equation this phenomenon is expected to be observable for electromagnetic wave propagation. Experimental data of electromagnetic wells realized by wave guides filled with different dielectrics confirm this conjecture now.Comment: 10 pages, 6 figure

Induced roughness in thin films of smectic-

The surface topography of a thin homeotropically oriented film of ferroelectric smectic-C* elastomer is studied by atomic force microscopy. We find that when the film is mechanically stretched, its surface becomes increasingly rough, in proportion to the applied strain. The effect depends strongly on the nature of crosslinks forming the elastomer network. The r.m.s. roughness correlations show a consistent trend $\langle [h(x)-h(0)]^2\rangle ^{1/2} \sim (x/\xi)^{0.5}$. We introduce a theoretical model assuming that random disorder in the smectic tilt angle is induced by deformations via the coupling of mesogens to the elastic network. The model describes the observed power law and gives a prediction for the correlation length ξ