Spin-orbit torque rectifier for energy harvesting from weak radio-frequency

We will discuss a new application of materials exhibiting spin-orbit torque, especially in radio detection, and particularly for harvesting ambient weak radio signals, where conventional technologies fail to operate. We propose a rectifier concept, simultaneously utilizing the spin-orbit torque and the Hall effect, that can provide 100 μV DC voltage from a 500 nW of radio-frequency (RF) power using existing materials, with a power conversion efficiency as high as 71%. The DC voltage strength can be efficiently enhanced to 100 mV from the same RF power with a series array of such devices while matching the low impedance of the receiver antenna. The Hall effect and spin-orbit-torque are both proportional to current density, which improves inversely with device cross-sectional area, providing the largest signals at the nanoscale. The proposed device can lead to important new technologies addressing the alarming energy issues in the era of the internet-of-things, wearable devices, and densely integrated 3D circuits.