Approaching to low thermal conductivity limit in layered materials through full-spectrum phonon band engineering

Abstract

Exploring the lower bound of thermal conductivity in fully dense solids holds significant fundamental and practical importance. Rotation stacked layered materials have been proven as a unique platform to achieve low thermal conductivity, but the reported performance should be partially attributed to the size effects of the ultrathin film. Here, we theoretically demonstrate the possibility of using full-spectrum phonon band engineering to achieve a through-plane thermal conductivity as low as 0.046 W m⁻¹ K⁻¹ in a sufficiently large rotation stacked MoS₂/WSe₂ structure, which is three orders of magnitude smaller than its bulk counterpart, MoS₂, and is among the lowest thermal conductivity values ever reported. We trace this behavior in the hetereostructure to the suppression of longitudinal acoustic phonon branch due to heavier atomic mass, and to the mass alternating induced increase of frequency intervals that effectively inhibits the energy hopping of localized high-frequency modes. We highlight the importance of suppression of the thermal conductivity from high-frequency vibrational modes, which usually lies outside of the conventional strategies of designing of low thermal conductivity materials. We also find that the hetereostructure has an extremely high thermal conductivity anisotropy ratio of 1150. This work provides new insight into the nature of thermal transport at a quantitative level and valuable guidelines for searching and designing new ultralow thermal conductivity material of potential interest for effective thermal management.