Published in Nature Communications, this research, led
Spin can be thought of as the rotation of an electron around its own axis. It is a form of intrinsic angular momentum and can be detected as a magnetic field with one of two orientations: up and down. Electron spin is difficult to handle and often loses direction over time. To use electron spin in a device, spin polarisation is important—this is the ability to control the fraction of electrons with a spin up or down. "Spin polarization can be achieved by sending the electrons through a ferromagnetic material," van Wees explains.
Professor van Wees and his team showed that they could greatly improve the efficiency of the injection and detection of spin electrons into graphene by using the insulator boron nitride in between the graphene layer and the ferromagnetic spin injector/detector electrodes.
"Graphene is a very good material for spin transport, but it does not allow one to manipulate the spins," says van Wees "To inject spins into the graphene, one has to make them pass from a ferromagnet through a boron nitride insulator by quantum tunnelling. We found that using a two-atom layer of boron nitride resulted in a very strong spin polarization of up to 70 percent, 10 times what we usually get."
In the devices produced, the polarisation increased with voltage, challenging the current thinking that it is only the ferromagnetic influence that polarises spin. Instead, it would seem that it is the quantum tunnelling that polarises the spin in his devices. The researchers also found a similar tenfold increase in spin detection in the same device. "So overall, the signal increased by a factor of 100," said van Wees.
Read more at: https://phys.org/news/2017-08-graphene-boron-nitride-heterostructure-large.html#jCp
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