Photo-induced lattice contraction in layered materials

Area of Science:

• Materials Science
• Condensed Matter Physics
• Computational Chemistry

Background:

• Optical excitation induces structural and electronic changes in 2D crystals, crucial for their functionalization.
• Understanding excited-state effects on both in-plane covalent and out-of-plane van der Waals bonds is key for tuning photo-response in anisotropic materials.
• Previous studies focused on in-plane dynamics, leaving the impact on weak interlayer interactions less explored.

Purpose of the Study:

• To investigate atomic motion in photoexcited molybdenum disulfide (MoS2) bilayers using non-adiabatic quantum molecular dynamics.
• To characterize the influence of electronic excitation on the out-of-plane van der Waals interactions in MoS2 bilayers.

Main Methods:

• Utilized non-adiabatic quantum molecular dynamics simulations.
• Investigated atomic motion in photoexcited MoS2 bilayers.
• Analyzed structural changes within 100 femtoseconds (fs) post-excitation.

Main Results:

• Observed a significant, nonthermal reduction in the out-of-plane lattice parameter of MoS2 bilayers.
• This structural change occurred rapidly, within 100 fs of electronic excitation.
• The reduction is attributed to electron redistribution into excited states with reduced anti-bonding character between layers.

Conclusions:

• Electronic excitation strongly affects weak out-of-plane van der Waals bonds in MoS2 bilayers.
• This nonthermal modulation of interlayer interactions presents potential applications.
• The findings could guide property modulation in layered materials and polymers with non-covalent interactions.