Driving forces for ultrafast laser-induced sp2 to sp3 structural transformation in graphite

Understanding the microscopic mechanism of photoinduced sp(2)-to-sp(3) structural transformation in graphite is a scientific challenge with great importance. Here, the ultrafast dynamics and characteristics of laser-induced structural transformation in graphite are revealed by non-adiabatic quantum dynamic simulations. Under laser irradiation, graphite undergoes an interlayer compression and sliding stage, followed by a key period of intralayer buckling and interlayer bonding to form an intermediate sp(2)-sp(3) hybrid structure, before completing the full transformation to hexagonal diamond. The process is driven by the cooperation of charge carrier multiplication and selective phonon excitations through electron-phonon interactions, in which photoexcited hot electrons scattered into unoccupied high-energy conduction bands play a key role in the introduction of in-plane instability in graphite. This work identifies a photoinduced non-adiabatic transition pathway from graphite to diamond and shows far-reaching implications for designing optically controlled structural phase transition in materials.

Automated summary

In this work, the ultrafast dynamics and characteristics of laser-induced structural transformation in graphite are revealed by non-adiabatic quantum dynamic simulations. It is found that graphite undergoes an interlayer compression and sliding stage, followed by a key period of intralayer buckling and interlayer bonding to form an intermediate sp(2)-sp(3) hybrid structure, before completing the full transformation to hexagonal diamond. The process is driven by the cooperation of charge carrier multiplication and selective phonon excitations through electron-phonon interactions, with photoexcited hot electrons playing a key role in introducing in-plane instability in graphite. This work identifies a photoinduced non-adiabatic transition pathway from graphite to diamond and has important implications for designing optically controlled structural phase transition in materials.