In recent years there has been a number of proposals of thermal devices operating in the near-field regime that make use of phase-transition materials. Here, we present a theoretical study of near-field thermal diodes and transistors that combine superconducting materials with normal (nonsuperconducting) metals. To be precise, we show that a system formed by two parallel plates made of $\mathrm{Nb}$ and $\mathrm{Au}$ can exhibit unprecedented rectification ratios very close to unity at temperatures around the $\mathrm{Nb}$ superconducting critical temperature and for a wide range of gap size values within the near-field regime. Moreover, we also show that a superconducting $\mathrm{Nb}$ layer placed between $\mathrm{Au}$ plates can operate as a near-field thermal transistor where the amplification factor can be greatly tuned by varying different parameters such as the temperature and thickness of the $\mathrm{Nb}$ layer or the distance between the $\mathrm{Nb}$ layer and the $\mathrm{Au}$ plates. Overall, our work shows the potential of the use of superconductors for the realization of near-field thermal devices.

• Received 20 November 2020
• Revised 14 January 2021
• Accepted 29 January 2021

DOI:https://doi.org/10.1103/PhysRevApplied.15.024036