Picosecond dynamics of laser-induced strain in graphite

Abstract

We report on the use of grazing-incidence time-resolved x-ray diffraction to investigate the evolution of strain in natural graphite excited by femtosecond-laser pulses in the fluence range of 6-35 mJ/cm 2 . Strains corresponding to up to ∼2.8% c-axis expansion were observed. We show that the experimental data is in good agreement with calculations based on the Thomsen strain model in conjunction with dynamical diffraction theory. Furthermore we find no evidence of nonthermal lattice expansion as reported in recent ultrafast electron-diffraction studies of laser-excited graphite conducted under comparable excitation conditions.

Observing (non)linear lattice dynamics in graphite by ultrafast Kikuchi diffraction

“…Although the elastic properties of graphite and other carbon allotropes have been investigated for decades (6), a comprehensive and complete picture (7)(8)(9) still is lacking, especially when describing the nonlinear elastic properties, whose measurement requires homogeneous and large specimens (8).…”

Coherent and Incoherent Electron-Phonon Coupling in Graphite Observed with Radio-Frequency Compressed Ultrafast Electron Diffraction

“…Experiments performed at a larger angle (π/8 > φ > π/4) revealed statistically significant lattice expansion and coherent phonon signatures. Coherent vibrations and lattice expansion dynamics have previously been observed in UED and UXD experiments [22][23][24][25].…”

Anisotropic electron-phonon coupling investigated by ultrafast electron crystallography: Three-temperature model

“…Such interesting observation has led to the assumption that SCOPs might be involved in the carrier generation process to directly channel optical energy in to the lattice 31,45 . Second, the various timescales reported for hot phonon relaxations, which range from 1 to 7 ps 31,48,56 must be reconciled with the time scale of lattice heating [57][58][59] .…”