Electrical spin filtering the key to ultra-fast, energy-efficient
spintronics
Electrical spin filtering avoids energy-costs of magnetic field

Date:
December 4, 2020
Source:
ARC Centre of Excellence in Future Low-Energy Electronics
Technologies
Summary:
A new study is a step towards even-faster, more energy-efficient
'spintronic' technology - an exciting, beyond-CMOS technology. The
new study applies 'spin-filtering' to separate spin orientation,
allowing generation and detection of spin via electrical (rather
than magnetic) means, because electric fields are a lot less
energetically costly to generate than magnetic fields.



FULL STORY ========================================================================== Spin-filtering could be the key to faster, more energy-efficient
switching in future spintronic technology, allowing the detection of
spin by electrical rather than magnetic means.


==========================================================================
A UNSW paper published last month demonstrates spin detection using a
spin filter to separate spin orientation according to their energies.

Ultra-fast, ultra-low energy 'spintronic' devices are an exciting,
beyond-CMOS technology.

DETECTING SPIN VIA ELECTRICAL MEANS IN FUTURE SPINTRONICS The emerging
field of spintronic devices use the extra degree of freedom offered
by particles' quantum spin, in addition to its charge, allowing for
ultra-fast, ultra-low energy computation.

The key is the ability to generate and detect spin as it accumulates on
a material's surface.



==========================================================================
The aim of researchers is to generate and detect spin via electrical
means, rather than magnetic means, because electric fields are a lot
less energetically costly to generate than magnetic fields.

Energy-efficient spintronics is dependent on both generation and detection
of spin via electrical means.

In strongly spin-orbit coupled semiconductor systems, all-electrical
generation of spin has already been successfully demonstrated.

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

In this new study, UNSW researchers have exploited the non-linear
interactions between spin accumulation and charge currents in
gallium-arsenide holes, demonstrating all-electrical spin-to-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, generation and detection of spin accumulation in
semiconductors has been achieved through optical methods, or via the
spin Hall effect-inverse spin Hall effect pair.

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

ALL-ELECTRICAL SPIN FILTERING The UNSW study introduces a new method
for detecting spin accumulation -- using a spin filter, which separates different spin orientations based on their energies.

Typically, spin filters have relied on the application of large magnetic fields, which is impractical and can interfere with the spin accumulation.

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

"Using ballistic, mesoscopic gallium-arsenide holes as a model system for strongly spin-orbit coupled materials, we demonstrated non-linear spin-to- charge conversion that is all-electrical and requires no magnetic field,"
says corresponding author A/Prof Dimi Culcer (UNSW).

"We showed that non-linear spin-to-charge conversion is fully consistent
with the data obtained from linear response measurements and is orders
of magnitude faster," says corresponding-author Prof Alex Hamilton,
also at UNSW.

Because the non-linear method does not need a magnetic field nor a long
spin diffusion length, it promises new possibilities for fast detection
of spin accumulation in strongly spin-orbit coupled materials with short
spin diffusion lengths, such as TMDCs and topological materials.

Finally, the rapidness of non-linear spin-to-charge conversion can
enable time- resolved read-out of spin accumulation down to 1 nanosecond resolution.


========================================================================== Story Source: Materials provided by ARC_Centre_of_Excellence_in_Future_Low-Energy_Electronics
Technologies. Note: Content may be edited for style and length.


========================================================================== Journal Reference:
1. E. Marcellina, A. Srinivasan, F. Nichele, P. Stano, D. A. Ritchie,
I.

Farrer, Dimitrie Culcer, A. R. Hamilton. Nonlinear spin filter for
nonmagnetic materials at zero magnetic field. Physical Review B,
2020; 102 (14) DOI: 10.1103/physrevb.102.140406 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2020/12/201204110229.htm

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