Half-auxetic effect and ferroelasticity in a two-dimensional monolayer TiSe

Area of Science:

• Materials Science
• Condensed Matter Physics
• Nanotechnology

Background:

• Two-dimensional (2D) materials with combined auxetic and ferroelastic properties are scarce.
• Such materials hold significant promise for next-generation microelectromechanical and nanoelectronic systems.

Purpose of the Study:

• To investigate the presence of both half-auxetic effect and ferroelasticity in a single p2mm-type TiSe monolayer.
• To elucidate the underlying mechanisms responsible for these unique properties.

Main Methods:

• First-principles calculations were employed to study the TiSe monolayer.
• Analysis involved examining nearest and next-nearest neighbor interactions to understand the auxetic behavior.
• The ferroelasticity was attributed to the Jahn-Teller effect on Ti atoms.

Main Results:

• A novel half-auxetic effect was observed in the TiSe monolayer, where it expands laterally under both tensile and compressive uniaxial strain.
• Ferroelasticity was identified and linked to the degeneracy breaking of Ti 3d-orbitals in a distorted crystal field.
• The study provides a fundamental understanding of the interplay between strain and electronic structure in 2D materials.

Conclusions:

• The p2mm-type TiSe monolayer exhibits an extraordinary combination of half-auxetic effect and ferroelasticity.
• These findings pave the way for designing novel 2D materials with multiple functionalities for advanced electronic applications.
• The research offers a design guideline for future nanoscale multifunctional materials.