Materials Science. Non-Equilibrium Phase Transformations.
Vol. 12 (2026), Issue 1, pg(s) 33-38

Ultrafast bond softening and non-thermal phase dynamics in femtosecond-excited diamond

  • 1 Institute for Nuclear Research and Nuclear Energy , Bulgarian Academy of Sciences, Bulgaria; Institute for Advanced Physical Sciences, New Bulgarian University, Bulgaria

Abstract

This work presents a first-principles theoretical investigation into the ultrafast non-equilibrium dynamics, optical breakdown, and structural response of bulk diamond irradiated by intense 12-fs laser pulses with 400 nm wavelength. By modeling transient electron density dynamics, energy deposition, internal electric fields, and transient dielectric functions, we map the microscopic pathways leading to ultrafast non-thermal phase transitions and surface patterning. For low intensities, photoinoziation of diamond follows the predictions of the perturbative non-linear optics, and a qualitative change of the electron dynamics occurs when the laser intensity increases above 5×〖10〗^14 W⁄〖cm〗^2 . We find that in this high intensity regime, laser energy absorption is enhanced due to excitation of bulk plasmon resonance. The electron density difference distribution shows the effect of softening of C-C bonds: the charge density in the binding region is not sufficient to balance the nuclear repulsion forces, resulting in instability of the diamond lattice.

Keywords

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