Anomalous in-plane lattice thermal conductivity in an atomically thin two-dimensional α-GeTe layer

Area of Science:

• Condensed Matter Physics
• Materials Science

Background:

• Low lattice thermal conductivity is essential for phononic device applications.
• Understanding thermal transport in 2D materials is critical for advanced technologies.

Purpose of the Study:

• Investigate the in-plane lattice thermal conductivity of monolayer and bilayer α-GeTe.
• Analyze the contribution of different phonon modes to thermal conductivity.

Main Methods:

• First-principles calculations were employed to study thermal transport properties.
• Analysis of phonon modes and Grüneisen parameters was performed.

Main Results:

• Monolayer α-GeTe showed lattice thermal conductivity of 0.43 W mK⁻¹ (zigzag) and 0.21 W mK⁻¹ (armchair) at 300 K.
• Bilayer α-GeTe exhibited significantly suppressed conductivity: 0.044 W mK⁻¹ (zigzag) and 0.047 W mK⁻¹ (armchair) at 300 K.
• The out-of-plane acoustic mode in bilayer α-GeTe has a large Grüneisen parameter, leading to ultralow thermal conductivity, with optical modes dominating.

Conclusions:

• Bilayer α-GeTe demonstrates ultralow in-plane lattice thermal conductivity, making it a promising material for phononic devices.
• The findings suggest potential applications in thermoelectric devices and heat insulators.
• Further experimental verification of these theoretical predictions is encouraged.