Nonlinear light absorption in Ti₃C₂T _x MXene: a theoretical study.

Area of Science:

• Materials Science
• Condensed Matter Physics
• Nanotechnology

Background:

• MXenes exhibit nonlinear absorption, enabling applications in ultrafast photonics, particularly in mode-locked fiber lasers.
• Current theoretical models use a two-level system approximation, requiring parameter fitting and neglecting MXene band structure.

Purpose of the Study:

• To theoretically investigate the microscopic origin of nonlinear absorption in MXenes.
• To develop a more accurate model for nonlinear absorption in MXenes by incorporating their band structure.

Main Methods:

• Utilized published band structure calculations for titanium carbide (Ti3C2) MXene.
• Applied density matrix theory within a two-band model and resonance approximation.
• Calculated the nonlinear absorption coefficient.

Main Results:

• Developed a theoretical framework to explain nonlinear absorption in MXenes based on their band structure.
• The model provides insights into the microscopic mechanisms governing saturation dynamics.
• Discussed recent experimental nonlinear transmittance data within this new theoretical framework.

Conclusions:

• The two-band model incorporating band structure offers a more fundamental understanding of MXene nonlinear absorption.
• This work elucidates the microscopic character of saturation dynamics in MXenes.
• Provides a foundation for designing MXene-based optical devices with tailored nonlinear responses.