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Detecting and Producing a Spin Current in Germanium

​A team from INAC has successfully carried out the conversion of a spin current into a charge current at the interface between iron and germanium, thanks to spin–orbit coupling. According to the reciprocity principle, the reverse process is also possible. This result implies that the generation and detection of a spin current are a priori feasible with current CMOS technology. It constitutes a first step toward a spin transistor relying entirely on spin–orbit coupling.

Published on 1 March 2017

"Spin-orbit coupling" is a relativistic effect that affects the electron spin by the mere presence of the atomic nucleus and, more generally, by its environment. Used in heavy metals, this effect would eventually make it possible to write on an MRAM. In contrast, it is practically absent in silicon and germanium, the main materials used in microelectronics. A technique of molecular beam epitaxy at low temperature, implemented at INAC, now allows the obtaining of very clean, even flawless, interfaces between iron and germanium, where a strong spin-orbit coupling called Rashba can emerge.

The physicists from INAC used this interface as a spin separator. In the case of an incident spin current, the Rashba effect then generates an electric voltage at the interface between the two materials. The spin current is, therefore, converted into a classical electric charge current.

This work was conducted in collaboration with Unité Mixte de Physique CNRS/Thales in Palaiseau, France, and the Jülich Research Center in Germany.

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