Berlin 2012 – wissenschaftliches Programm

Bereiche | Tage | Auswahl | Suche | Aktualisierungen | Downloads | Hilfe

MM: Fachverband Metall- und Materialphysik

MM 22: Functional Materials I

MM 22.5: Vortrag

Dienstag, 27. März 2012, 11:15–11:30, H 1029

Three displacively excited coherent phonons in infinite BN nanotubes — •Bernd Bauerhenne, Eeuwe Zijlstra, and Martin Garcia — Theoretische Physik - Universität Kassel, Heinrich-Plett-Str. 40, 34132 Kassel, Germany

BN nanotubes are isostructual to carbon nanotubes with boron and nitrogen atoms occupying the even and odd sublattices, respectively. They are described by the so called wrapping vector, which defines how the hexagonal sheet is cut off and rolled up. The wrapping vector also divides the tubes into the three groups: armchair, zizag and chiral. In particular, we investigate the excitation of a (5,0) zigzag BN nanotube with an intense ultrashort laser pulse by means of ab initio molecular dynamics simulations on laser-excited potential energy surfaces. Our results show that only three phonon modes are simultaneously excited. We identify these three modes as the radial breathing mode, the radial buckling mode and the longitudinal bond stretching mode. The frequencies of the three modes show a softening for increasing laser intensity. The analysis of our results show, that we can describe all effects of the laser excitation by a three-dimensional harmonic oscillator. Using this model we analyse the possibility to steer the excitation of the three modes by using, instead of one, two or three pump laser pulses.