Magneto‐Tunable Thermal Diode Based on Bulk Superconductor

Abstract The thermal diode is a growing technology and is important for active thermal flow control. Since the theoretical designing of thermal diode in 2004, various kinds of solid‐state thermal diodes have been theoretically and experimentally investigated. Here, thermal rectification in bulk‐size superconductor–normal metal junctions is reported. High‐purity (5N) wires of Pb and Al are soldered, and the thermal conductivity ( κ ) of the junctions is measured in two different directions of the heat flow, forward ( κ F ) and reverse ( κ R ) directions. Thermal rectification ratio ( κ F / κ R ) of 1.75 is obtained at T ∼ 5.2 K with H = 400 Oe. The merit of the Pb–Al junction is a large difference of κ in the order of several hundred W m −1 K −1 and magneto‐tunability of the working temperature.