Theory for Negative Thermal Transport: Complex Thermal Conductivity

Abstract

AbstractIn this chapter, we coin a complex thermal conductivity whose imaginary part corresponds to the real part of a complex refractive index. Therefore, the thermal counterpart of a negative refractive index is just a negative imaginary thermal conductivity, featuring the opposite directions of energy flow and wave vector in thermal conduction and advection, thus called negative thermal transport herein. We design an open system with energy exchange and explore three different cases to reveal negative thermal transport to avoid violating causality. We further provide experimental suggestions with a solid ring structure. All finite-element simulations agree with the theoretical analyses, indicating that negative thermal transport is physically feasible. These results have potential applications such as designing the inverse Doppler effect in thermal conduction and advection.