Electric spin filtering: the key to ultra-fast and energy-efficient spintronics

Spin filtering could be the key to faster and more energy-efficient switching in future spintronics technology, allowing spin detection by electrical rather than magnetic means.

A UNSW article published last month demonstrates spin detection using a spin filter to separate the orientation of the spin based on their energies.

Ultra-fast, ultra-low-energy “spintronics” devices are an exciting technology, beyond CMOS.

Spin detection via electrical means in the future spintronics

The emerging field of spintronic devices uses the additional degree of freedom offered by the quantum spin of particles, in addition to its charge, allowing ultra-fast and very low energy computation.

The key is the ability to generate and sense rotation as it builds up on the surface of a material.

The researchers’ goal is to generate and detect the spin by electric means, rather than by magnetic means, since electric fields are much less energy-intensive to generate than magnetic fields.

Energy efficient spintronics depends on both generation and detection of the spin by electrical means.

In strongly coupled spin-orbit semiconductor systems, fully electric spin generation has already been successfully demonstrated.

However, the detection of spin-to-charge conversion has always required a wide range of magnetic fields, thus limiting speed and convenience.

In this new study, UNSW researchers exploited the nonlinear interactions between spin accumulation and charge currents in gallium arsenide holes, demonstrating fully electric spin-charge conversion without the need for a magnetic field.

“Our technique promises new possibilities for rapid spin detection in a wide variety of materials, without using a magnetic field,” explains lead author Dr. Elizabeth Marcellina.

Previously, the generation and detection of spin accumulation in semiconductors was accomplished by optical methods, or via the reverse spin Hall-spin-Hall effect pair.

However, these methods require a large spin scattering length, which means that they are not applicable to strongly coupled spin-orbit materials with a short spin scattering length.

Fully electric spin filtering

The UNSW study introduces a new method of detecting spin accumulation – using a spin filter, which separates different spin orientations based on their energies.

Typically, spin filters rely on the application of strong magnetic fields, which is inconvenient and can interfere with spin accumulation.

Instead, the UNSW team exploited nonlinear interactions between spin accumulation and charge, which facilitate the conversion of spin accumulation into charge currents even at zero magnetic field.

“Using ballistic and mesoscopic gallium-arsenide holes as a model system for strongly coupled spin-orbit materials, we have demonstrated a non-linear spin-charge conversion that is fully electric and requires no magnetic field,” says the author. correspondent A / Prof Dimi Culcer (UNSW).

“We have shown that the nonlinear spin-charge conversion is perfectly consistent with the data obtained from the linear response measurements and is an order of magnitude faster,” explains the corresponding author, Professor Alex Hamilton, also at UNSW.

Because the nonlinear method does not require a magnetic field or a long spin scattering length, it promises new possibilities for the rapid detection of spin accumulation in strongly coupled spin-orbit materials. with short spin diffusion lengths, such as TMDCs and topological materials.

Finally, the speed of the nonlinear spin-charge conversion can allow a time-resolved reading of the spin accumulation up to a resolution of 1 nanosecond.

Provided by ARC Center of Excellence in Future Low-Energy Electronics Technologies (FLEET)