Berlin 2012 – wissenschaftliches Programm
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DF: Fachverband Dielektrische Festkörper
DF 5: Electrical, mechanical and electromechanical properties
DF 5.1: Vortrag
Montag, 26. März 2012, 16:05–16:25, EB 107
Calibrated real time detection of nonlinearly propagating giant strain waves — •André Bojahr1, Marc Herzog1, Daniel Schick1, and Matias Bargheer1,2 — 1Institut für Physik und Astronomie, Universität Potsdam, Karl-Liebknecht-Str. 24-25, 14476 Potsdam, Germany — 2Helmholtz-Zentrum Berlin für Materialien und Energie GmbH, Wilhelm-Conrad-Röntgen Campus, BESSY II, Albert-Einstein-Str. 15, 12489 Berlin, Germany
Epitaxially grown metallic oxide films excited by femtosecond laser pulses can generate giant strain amplitudes on the order of 1% strain. We calibrate these transient strain amplitudes by ultrafast X-ray diffraction (UXRD). In addition we use picosecond reflectivity measurements to determine the speed of the propagating strain fronts by interference effects which are equivalent to stimulated Brillouin scattering [1]. For high strain amplitudes we observe two components of the sound pulses which travel at different sound speeds. We conclude that at giant strain amplitudes the compressive and tensile strain components travel at different sound velocities [2]. This is indicative of an anharmonic interaction between the atoms forming the crystal lattice which give rise to nonlinearities in the wave equation.
[1] Thomsen et al., Phys. Rev. B 34, 4129 (1986)
[2] P. J. S. van Capel and J. I. Dijkhuis, Appl. Phys. Lett 88, 151,910 (2006).