Dresden 2006 – wissenschaftliches Programm

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MM: Metall- und Materialphysik

MM 24: Quasicrystals

MM 24.5: Vortrag

Mittwoch, 29. März 2006, 15:00–15:15, IFW D

Structure factor of the dynamic Fibonacci chain — •Michael Engel, Steffen Sonntag, Hansjörg Lipp, and Hans-Rainer Trebin — Universität Stuttgart, Institut für Theoretische und Angewandte Physik, 70550 Stuttgart

We have constructed an anharmonic chain, denoted "dynamic Fibonacci chain", where neighbouring atoms interact by double-well potentials. Thus they are able to perform both harmonic motions and phason flips where short and long atomic separations are exchanged. Molecular dynamics simulations show that the difference between the coherent and incoherent structure factors of the dynamic and the harmonic Fibonacci chain is in general tiny and has the form of a characteristic broadening of the phonon branches. We ascribe it to the phasons flips. The temperature dependence of the broadening is discussed. Attempts are made to filter out the flip dynamics by suppressing the harmonic motion. If a bias is introduced in the well depth, broadened optic phonon bands split off. In direct space we observe correlated phason flips propagating with phonon excitations.