Periodic Amplification of Radiative Heat Transfer

The thermal excitation of materials with a periodic heat flux or temperature modulated in time is a reliable and accurate tool usually applied to determine thermal properties, through techniques such as thermoreectance, photothermal radiometry, 3ω, photoacoustics, thermal-wave resonant cavity, etc. Moreover, over the past years, the control of heat flux has been improved by means of phase-change materials (PCMs), whose internal structures are strongly driven by their temperature, which results in significant variations of their thermal [1], optical [2], and electrical [1] properties. Thermochromic materials (VO
₂
, nitinol) or superconductors are examples of such PCMs, where the material can be either in an insulator phase, with low thermal/electrical conductivity and high emissivity, or in a metallic one characterized by a high thermal/electrical conductivity and low emissivity. This metal-insulator transition (MIT) occurs at the critical temperature of each PCM and can therefore be used to tune the heat currents that the PCM exchanges with the environment, which paves the wave for novel applications.