When introducing pure spin into chiral materials, direction is important

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Schematic diagram of spin current absorption through achiral and chiral channels and properties of L-Co, D-Co, and M-Co thin films. Credit: Science Advances (2024). DOI: 10.1126/sciadv.adn3240

Researchers from North Carolina State University and the University of Pittsburgh studied how electron spin information, called pure spin current, moves through chiral materials. They found that the direction of spin injection into the chiral material affected the ability of the chiral material to pass through. These chiral “gates” can be used to design energy-efficient spintronic devices for data storage, communications, and computing.

Spintronic devices utilize the spin of electrons, not their charge, to generate current and move information through electronic devices.

“One of the goals of spintronics is to move spin information through a material without having to move the associated charge, because moving charge requires more energy—which is why your cell phone and computer get hot when you use them for a long time,” said David Waldeck, a chemistry professor at the School Kenneth P. Dietrich Arts and Sciences at Pitt and a co-author of the paper.

Chiral solids are materials that cannot be superimposed on them mirror image—Think of your left and right hands, for example. Left-handed gloves don’t fit on right hands, and vice versa. Chirality in spintronic materials allows researchers to control the direction of spin within the material.

“Before this research was conducted, it was thought that the chirality, or ‘chirality’, of a material was very important in determining how and whether spin would move through the material,” said Dali Sun, associate professor of physics, member of the Organic and Carbon Electronics Lab (ORaCEL) at North Carolina State University and co-author of the work.

“And when you move all the electrons through the material, that’s still true. But we found that if you inject pure spin into a chiral material, the spin current absorption depends strongly on the angle between the spin polarization and the chiral axis; in other words, whether the spin polarization is parallel or perpendicular to the chiral axis.”

“We used two different approaches, microwave particle excitation and ultrafast laser heating, to inject pure spin into the chiral materials chosen in this study, and both approaches gave us the same conclusion,” said Jun Liu, associate professor of engineering and mechanical engineering. . aerospace engineeringmember of ORaCEL at NC State and co-author of the work.

“The chiral materials we chose are two thin films of chiral cobalt oxide, each with different chiral, or ‘handedness’, properties,” Liu said. “Non-chiral cobalt oxide thin films are commonly used in modern electronics.”

When the team injected pure spins aligned perpendicular to the chiral axis of the material, they noted that the spins did not move through the material. However, when pure spin is aligned parallel or anti-parallel to the chiral axis, its absorption, or ability to pass through the material, increases by 3000%.

“Because spin can only pass through these chiral materials in one direction, this allows us to design chiral gates for use in electronic devices,” Sun said. “And this research also challenges some of what we thought we knew about chiral materials and spin, which is something we want to explore further.”

The work appears in Science Advances. NC State postdoctoral researcher Rui Sun, NC State graduate student Ziqi Wang, and University of Pittsburgh Research Assistant Professor Brian Bloom are co-first authors.

Further information:
Rui Sun et al, Colossal anisotropic absorption of spin currents induced by chirality, Science Advances (2024). DOI: 10.1126/sciadv.adn3240

Prepared by
North Carolina State University

Quotation: When injecting pure spin into chiral materials, important directions (2024, May 4) retrieved May 4, 2024 from https://phys.org/news/2024-05-pure-chiral-materials.html

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