Direct observation of optically induced transient structures in graphite using ultrafast electron crystallography

Abstract

We use ultrafast electron crystallography to study structural changes induced in graphite by a femtosecond laser pulse. At moderate fluences of ~< 21mJ/cm^2, lattice vibrations are observed to thermalize on a time scale of ~8ps. At higher fluences approaching the damage threshold, lattice vibration amplitudes saturate. Following a marked initial contraction, graphite is driven nonthermally into a transient state with sp^3-like character, forming interlayer bonds. Using ab initio density functional calculations, we trace the governing mechanism back to electronic structure changes following the photo-excitation.

5 pages, 4 figures; to appear in Phys. Rev. Lett

References in corpus (2)

• Ab initio simulations of excited carrier dynamics in carbon nanotubes
• Photovoltage Dynamics of the Hydroxylated Si(111) Surface Investigated by Ultrafast Electron Diffraction