Electrically-tunable near-field heat transfer with ferroelectric materials

Abstract

Radiative heat transfer at small separations can be enhanced by orders of magnitude via the use of surface phonon polariton or plasmon polariton waves. This enhancement has potential applications in different devices, such as thermal emitters, thermal rectifiers, thermophotovoltaic and thermoelectric energy conversion systems. In this thesis, the author explores the tunable optical properties of ferroelectric materials to manipulate the near-field radiative heat transfer between two surfaces, aiming at the active control of near-field radiation heat transfer. Soft mode hardening of ferroelectric thin films induced by environmental changes, such as temperature and electric field, is widely used as a basis for tunable and switchable electrical and optical devices. However, this mechanism has not yet been examined for heat transfer applications. Using the fluctuation-dissipation theorem and the Dyadic Green's function method, the author shows via simulation that the magnitude and spectral characteristics of radiative heat transfer can be tuned via an externally applied electric field and temperature. Ways are explored to maximize the tuning contrast and discuss the trade-off between maximizing tunability and heat transfer. Our simulation results suggest that ferroelectrics can be used to develop new types of tunable nano-scale devices for thermal and energy conversion applications.