Can Light Program Electronics?

What if the color of light could determine not only what we see, but how an electric current behaves?

Spintronics seeks to exploit not only the charge of the electron but also its spin, promising devices that are faster, denser and more energy-efficient than today's electronics. The practical obstacle has been generating spin-polarized currents in a semiconductor without an external magnetic field.

A new international study, led jointly by Prof. Doron Naveh of Bar-Ilan University and the Bar-Ilan Institute of Nanotechnology and Advanced Materials (BINA), Prof. Efrat Lifshitz of the Technion - Israel Institute of Technology and Prof. Thomas Heine of TU Dresden, together with Rajesh Kumar Yadav, Michal Poplinger, Adi Levi, Adi Harchol, Nirman Chakraborty and Thomas Brumme, proposes a different control knob: the wavelength of the light itself.

The researchers built a van der Waals heterostructure pairing the antiferromagnetic semiconductor NiPS3 with WSe2 in a p-n diode configuration, and illuminated it with circularly polarized light.

Illumination produces photoconductive resonances in which a large share of the photogenerated carriers take the same spin orientation. The authors report spin polarization approaching 80 percent near the Neel temperature and roughly 30 percent at room temperature, and find that selected spectral bands retain the sign of their polarization across the magnetic phase transition.

In other words, the spin direction can be selected by tuning the wavelength of the light, with no magnetic field and no switching of the light's polarization. Polarization-resolved photogalvanic measurements point to a circular injection-current mechanism, while first-principles calculations indicate that an applied electric field drives interfacial hybridization and spin-layer locking at the interface.

This is fundamental research performed on a laboratory device rather than a product. Its significance lies in the principle it establishes: that a basic property of light, its color, can serve as a programming input for a spin-based electronic system, opening a path for opto-spintronics.

Congratulations to Prof. Doron Naveh and his research partners on a notable scientific achievement and a new direction in spintronics.

Read the full paper published in Advanced Materials: https://doi.org/10.1002/adma.74889