Unusually low thermal conductivity of atomically thin 2D tellurium

Abstract

Tellurium is a high-performance thermoelectric material due to its superior electronic transport and low lattice thermal conductivity (κ_L). Here, we report the ultralow κ_L in the monolayer tellurium, i.e., tellurene, which has been successfully synthesized in recent experiments. We find that tellurene has a compellingly low room temperature κ_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 κ_L to the soft acoustic modes, the extremely low-energy optical modes and the strong scattering among optical–acoustic phonons, which place tellurene as a potential novel thermoelectric material. Finally, we show that κ_L is proportional to the largest acoustic phonon frequency (ω^a_D) and the lowest optical phonon frequency at the Γ point (ω^o_Γ) in 2D materials, which reflect both harmonic and anharmonic thermal properties, respectively.