A phononic rectifier based on carbon schwarzite host–guest system

Thermal rectification is a promising way to manipulate the heat flow,in which thermal phonons are spectrally and collectively controlled.As phononic devices are mostly relying on monochromatic phonons,in this work we propose a phononic rectifier based on the carbon schwarzite host–guest system.By using molecular dynamic simulations,we demonstrate that the phononic rectification only happens at a specific frequency of the hybridized mode for the host–guest system,due to its strong confinement effect.Moreover,a significant rectification efficiency,~134%,is observed,which is larger than most of the previously observed efficiencies.The study of length and temperature effects on the phononic rectification shows that the monochromaticity and frequency of the rectified thermal phonons depend on the intrinsic anharmonicity of the host–guest system and that the on-center rattling configuration with weak anharmonicity is preferable.Our study provides a new perspective on the rectification of thermal phonons,which would be important for controlling monochromatic thermal phonons in phononic devices.

How coherence is governing diffuson heat transfer in amorphous solids

Thermal transport in amorphous materials has remained one of the fundamental questions in solid state physics while involving a very large field of applications.Using a heat conduction theory incorporating coherence,we demonstrate that the strong phase correlation between local and non-propagating modes,commonly named diffusons in the terminology of amorphous systems,triggers the conduction of heat.By treating the thermal vibrations as collective excitations,the significant contribution of diffusons,predominantly relying on coherence,further reveals interesting temperature and length dependences of thermal conductivity.The propagation length of diffuson clusters is found to reach the micron,overpassing the one of propagons.The explored wavelike behavior of diffusons uncovers the unsolved physical picture of mode correlation in prevailing models and further provides an interpretation of their ability to transport heat.This work introduces a framework for understanding thermal vibrations and transport in amorphous materials,as well as an unexpected insight into the wave nature of thermal vibrations.