Ultralow-Barrier Antiferroelectric-Ferroelectric Transition Enabled by Competing Polar Distortion in Two-Dimensional...

Area of Science:

• Materials Science
• Solid State Physics
• Computational Chemistry

Background:

• Two-dimensional (2D) Ruddlesden-Popper (RP) nitride perovskites offer unique properties for low-energy polarization control.
• Their reduced dimensionality and weak interlayer coupling are key to novel electronic functionalities.

Purpose of the Study:

• Investigate the ferroelectric (FE) and antiferroelectric (AFE) properties of the 2D RP nitride perovskite La2WN4.
• Explore the mechanisms of polarization switching and the impact of external stimuli.

Main Methods:

• Utilized first-principles calculations for theoretical analysis.
• Employed symmetry analysis and mode decomposition to understand structural and polarization behavior.

Main Results:

• Identified competing semiconducting FE (Aba2) and AFE (Pna21) phases in La2WN4.
• Demonstrated low energy barriers for AFE-FE interconversion and polarization reversal.
• Showcased reversible AFE/FE switching via 1% biaxial compressive strain or an in-plane electric field (0.025 V/Å).
• Confirmed exfoliation into a stable monolayer with sizable in-plane polarization and low switching barrier.

Conclusions:

• La2WN4 exhibits promising characteristics for fast, energy-efficient polarization switching.
• External stimuli effectively control the AFE/FE states.
• The stable monolayer form holds potential for low-power-programmable AFE/FE devices.