Virial stress unveils atomic strain governing interfacial thermal rectification

Abstract

Thermal rectification is a phenomenon in which heat flow exhibits a preferential direction and has attracted significant attention due to its potential applications in nanoscale thermal management, such as thermal transistors and switches. Various mechanisms have been proposed to explain thermal rectification, emphasizing different physical factors and leading to a system-dependent microscopic understanding. Based on the virial stress–strain relationship, we derive a mathematical expression that correlates thermal conductivity with statistical measures of atomic strain in nanoscale systems. Using non-equilibrium molecular dynamics simulations, we apply this framework to silicon–germanium heterojunctions with different crystal orientations, focusing on interface-driven thermal rectification. The results show that atomic strain near the interface plays a dominant role in determining the preferential direction of heat flow in these nanoscale heterostructures, providing a consistent interpretation beyond conventional analyses based on phonon vibrational density of states overlap. This strain-based perspective highlights the importance of interfacial effects in nanoscale thermal rectification and contributes to a clearer understanding of interface-dominated heat transport.