Efficient valves for electron spins

Date:
August 12, 2020
Source:
University of Basel
Summary:
Researchers have developed a new concept that uses the electron
spin to switch an electrical current. In addition to fundamental
research, such spin valves are also the key elements in spintronics
-- a type of electronics that exploits the spin instead of the
charge of electrons.



FULL STORY ========================================================================== Researchers at the University of Basel in collaboration with colleagues
from Pisa have developed a new concept that uses the electron spin
to switch an electrical current. In addition to fundamental research,
such spin valves are also the key elements in spintronics -- a type of electronics that exploits the spin instead of the charge of electrons. The results were published in the scientific journal Communications Physics.


==========================================================================
At some point, spintronics might become a buzzword that is as much a
part of our vocabulary as electronics. The idea behind it is to use
the angular momentum (spin) of an electron instead of the electrical
charge. Researchers around the world have been pursuing this goal for
many years. Spintronics promises numerous applications in information
storage and processing, and could improve the energy efficiency of
electronic devices. An important prerequisite is the efficient control
and detection of electron spins.

A team of physicists around Professor Christian Scho"nenberger and
Dr. Andreas Baumgartner from the Swiss Nanoscience Institute and the
Department of Physics at the University of Basel has now developed a
new technique for spintronics in semiconductor devices. Researchers from
the Instituto Nanoscienze-CNR in Pisa were also involved.

Nanomagnets are the key For this purpose, the scientists form two small semiconductor islands (quantum dots) behind each other on a nanowire and generate magnetic fields in the quantum dots using nanomagnets. Using
an external field, they are able to control these magnets individually
and thus can determine whether a quantum dot allows electrons to pass
with a spin directed upward (up) or downward (down).

When two quantum dots are connected in series, a current only flows if
both are set to "up" or both to "down." Ideally, no current flows if
they are oriented in opposite directions.

Arunav Bordoloi, first author of the publication and PhD student in the Scho"nenberger team, found that this method produced a spin polarization
close to the theoretical maximum. "With this technique, we can choose
whether a single electron in a given spin state is allowed to enter
or leave a quantum system -- with an efficiency far greater than in conventional spin valves," he says.

"In recent years, researchers around the world found it a hard nut to
crack to fabricate spin valves useful for nano- and quantum-electronic devices," says Dr. Andreas Baumgartner, who is supervising the
project. "We have now succeeded in producing one." Exploring new
phenomena The physicists were also able to show that the magnetic fields
are localized to specific locations on the nanowire. "This technique
should therefore allow us to study the spin properties of new phenomena typically too sensitive to magnetic fields, such as novel states at the
ends of special superconductors," comments Dr. Baumgartner.

This new approach to spintronics should now enable direct measurements of
spin correlations and spin entanglement and shed new light on many old
and new physical phenomena. In the future, the concept could even prove
useful in the quest to use electron spins as the smallest information unit (quantum bit) in a quantum computer.


========================================================================== Story Source: Materials provided by University_of_Basel. Note: Content
may be edited for style and length.


========================================================================== Journal Reference:
1. Arunav Bordoloi, Valentina Zannier, Lucia Sorba, Christian
Scho"nenberger, Andreas Baumgartner. A double quantum dot spin
valve.

Communications Physics, 2020; 3 (1) DOI: 10.1038/s42005-020-00405-2 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2020/08/200812115332.htm

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