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A new quantum system could help to develop better spintronics

Purdue University researchers used lasers to cool and cool atoms to near absolute zero. Then they become a quantum liquid known as Bose-Einstein condensate and collide with opposing condensates turning image credits: Purdue Quantum Center

Researchers have created a new field of quantum system testing in which they can literally turn certain particle interactions on and off, possibly paving the way for advances in spintronics.

Spin transport electronics have the potential to revolutionize electronic devices as we know them, especially when it comes to computers. While standard electronics use the charge of an electron to encode information, spintronic devices rely on another inherent property of the electron: its spin.

The spintronics could be faster and more reliable than conventional electronics because the spin can be changed quickly and these components consume less power. However, the field is young and there are many questions researchers need to solve to improve the control of spin information. One of the most complex issues facing the field is how the signal transmitted by spin-like particles, the so-called spin current, decays over time.

"The signal we need to get spintronics to work and study these things can crumble in. Just as we want a good cell phone service to make a call, we want that signal to be strong," said Chuan-Hsun Li, a student of Electrical Engineering and Computer Science at Purdue University. "When the spin current fades, we lose the signal." In the real world, electrons do not exist independently of everything around them and behave exactly as we expect. They interact with other particles and between different properties in themselves. The interaction between the spin of a particle (an intrinsic property) and the moment (an extrinsic property) is called a spin-orbit coupling.

According to a recent publication in Nature Communications Spin-orbit coupling and interactions With other particles, the spin current decay in a quantum fluid called Bose-Einstein condensate (BEC) can be dramatically increased.

"People want to manipulate spin formation so that we can use it to encode information, one possibility being physical mechanisms such as spin-orbit coupling," Li said. "However, this can lead to some disadvantages, such as loss of spin information. "

The experiment was conducted in the laboratory by Yong Chen, a professor of physics and astronomy, and electrical and computer engineering in Purdue team has created something like a mini-particle collider for BECs. Using lasers, rubidium-87 atoms were trapped in a vacuum chamber and cooled almost to absolute zero. (Physics junkies may remember that laser cooling technologies won the Nobel Prize in physics in 1

997. Laser trapping won the 2018 award.)

At this point, the atoms become a BEC: the coldest and most mysterious of the five states of matter , As the atoms get colder, they show wave-like properties. In this quantum state they have an identity crisis. They overlap and stop behaving like individuals. Although BEC is technically not a gas, this might be the simplest way to visualize the image – physicists sometimes refer to it as quantum fluid or quantum gas.

In the mini-quantum fluid collider, Chen's team sent two BECs with opposing spins into each other Like two gas clouds, they would partially penetrate each other and deliver a spin current.

"When you collide two condensates, they create many fascinating phenomena that were originally superfluous, but when they collide, this is part of the friction they can turn into thermal gas," Chen said. "Since we can control every parameter, this is a very efficient system for investigating this type of collision."

With this system, researchers can literally turn on and off spin-orbit coupling, which allows them to isolate their effect on spin current decay. This is not possible with electrons in solid state materials, which makes the system so powerful, Chen said.

So-called quantum gas is the cleanest system man can make. There is no perturbation that makes it possible to create a pure spin current and to study its properties. Chen hopes to continue using this experimental test field and its bosonic spin current to further explore many fundamental questions about spin transport and quantum dynamics.

"An important challenge for spintronics and other related quantum technologies is to reduce decay to spin information over longer distances for extended periods of time," he said. "With this new understanding of the role of spin-orbit coupling, this can help people gain new insights into reducing spin decay and potentially developing better Spintronic devices as well."

Explore further:
Electronics of the future: A new energy-efficient mechanism that uses the Rashba effect

Further information:
Chuan-Hsun Li et al., Spin current generation and relaxation in a quenched spin-orbit-coupled Bose-Einstein condensate, Nature Communications (2019). DOI: 10.1038 / s41467-018-08119-4

Magazine Reference:
Nature Communications

Provided by:
Purdue University

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