Theory for laser induced structural modification of carbon based materials

by Harald Jeschke, Inst. f. Theoretische Physik, Johann Wolfgang Goethe-Univ., Frankfurt/Main

Monday 30 Jun 2008, 15:00 → 16:00 Europe/Berlin

Bldg. 25f, Room 456

In many current problems of solid state physics, complex processes in the electronic system of materials and structural transitions occur simultaneously; both require a high level theoretical description. We investigate the ultrafast response of electrons and lattice following the excitation of a material by an intense femtosecond laser pulse by performing molecular dynamics simulations on time dependent potential energy surfaces. This method allows us to study the ultrafast melting and ablation of various forms of carbon, of silicon and germanium. Furthermore, it provides an opportunity to describe microscopic changes in structure below and close to the damage threshold of materials. The excitation of coherent phonons constitutes an especially interesting structural response. We find that they can be exploited in capped nanotubes to achieve a clean, nonthermal separation of cap and nanotube. We also show that laser induced nonequilibrium can induce defect healing processes in carbon nanostructures. Finally, we discuss possible extensions to our theoretical approach.