Unusually low thermal conductivity of atomically thin 2D tellurium

TL;DR

This paper reports the discovery of ultralow thermal conductivity in monolayer tellurium (tellurene), highlighting its potential as a thermoelectric material due to its unique phonon properties and scattering mechanisms.

Contribution

It provides the first experimental evidence of extremely low thermal conductivity in tellurene and links this property to specific phonon behaviors and frequencies.

Findings

Tellurene has a room temperature thermal conductivity of 2.16 and 4.08 W/mK.

The low thermal conductivity is due to soft acoustic modes and low-energy optical modes.

Thermal conductivity correlates with specific phonon frequencies, reflecting harmonic and anharmonic effects.

Abstract

Tellurium is a high-performance thermoelectric material due to its superior electronic transport and low lattice thermal conductivity ($\kappa_L$). Here, we report the ultralow $\kappa_L$ in the monolayer tellurium, i.e., tellurene, which has been successfully synthesized in recent experiments. We find tellurene has a compellingly low room temperature $\kappa_L$ of 2.16 and 4.08 W m$^{-1}$ K$^{-1}$ along the armchair and zigzag directions, respectively, which is lower than any reported values for other 2D materials. We attribute this unusually low $\kappa_L$ to the soft acoustic modes, extremely low-energy optical modes and the strong scattering among optical-acoustic phonons, which place tellurene as a potential novel thermoelectric material. Finally, we disclose that $\kappa_L$ is proportional to the largest acoustic phonon frequency ($\omega_{D}^{a}$) and the lowest optical phonon frequency at $\Gamma$ point ($\omega_{\Gamma}^{o}$) in 2D materials, which reflect both harmonic and anharmonic thermal properties respectively.