Rectification of electronic heat current by a hybrid thermal diode

A thermal diode with two orders of magnitude higher on/off ratio than that previously achieved can be obtained by combining normal metals and superconductors. Thermal diodes 1 , 2 —devices that allow heat to flow preferentially in one direction—are one of the key tools for the implementation of solid-state thermal circuits. These would find application in many fields of nanoscience, including cooling, energy harvesting, thermal isolation, radiation detection 3 and quantum information 4 , or in emerging fields such as phononics 5 , 6 , 7 and coherent caloritronics 8 , 9 , 10 . However, both in terms of phononic 11 , 12 , 13 and electronic heat conduction 14 (the latter being the focus of this work), their experimental realization remains very challenging 15 . A highly efficient thermal diode should provide a difference of at least one order of magnitude between the heat current transmitted in the forward temperature ( T ) bias configuration ( J fw ) and that generated with T -bias reversal ( J rev ), leading to ℛ = J fw / J rev ≫ 1 or ≪ 1. So far, ℛ ≈ 1.07–1.4 has been reported in phononic devices 16 , 17 , 18 , and ℛ ≈ 1.1 has been obtained with a quantum-dot electronic thermal rectifier at cryogenic temperatures 19 . Here, we show that unprecedentedly high ratios of ℛ ≈ 140 can be achieved in a hybrid device combining normal metals tunnel-coupled to superconductors 20 , 21 , 22 . Our approach provides a high-performance realization of a thermal diode for electronic heat current that could be successfully implemented in true low-temperature solid-state thermal circuits.