Researchers from North Carolina State University and the University of Pittsburgh studied how the spin information of an electron, called a pure spin current, moves through chiral materials. They found that the direction through which the spins are injected into chiral materials affects their ability to go through them. These chiral “gateways” may very well be used to design energy-efficient spintronic devices for data storage, communication and computing.
Spintronic devices harness the spin of an electron, reasonably than its charge, to create current and move information through electronic devices.
“One in all the goals in spintronics is to maneuver spin information through a fabric without also having to maneuver the associated charge, because moving the charge takes more energy — it’s why your phone and computer get hot while you use them for a very long time,” says David Waldeck, professor of chemistry in Pitt’s Kenneth P. Dietrich School of Arts and Sciences and co-corresponding writer of the work.
Chiral solids are materials that can’t be superimposed on their mirror image — consider your left and right hands, for instance. A left-handed glove doesn’t fit in your right hand, and vice-versa. Chirality in spintronic materials allows researchers to manage the direction of spin inside the material.
“Prior to this work, it was thought that the sense of chirality, or ‘handedness,’ of a fabric was very vital to how and whether the spin would move through that material,” says Dali Sun, associate professor of physics, member of the Organic and Carbon Electronics Lab (ORaCEL) at North Carolina State University and co-corresponding writer of the work.
“And while you’re moving the entire electron through the fabric that remains to be true. But we found that for those who inject pure spin right into a chiral material, the absorption of spin current strongly relies on the angle between the spin polarization and chiral axis; in other words, whether the spin polarization is aligned 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 chosen chiral materials on this study, and each approaches gave us the identical conclusion,” says Jun Liu, associate professor of mechanical and aerospace engineering, member of ORaCEL at NC State and co-corresponding writer of the work.
“The chiral materials we selected are two chiral cobalt oxide thin movies, each with a distinct chirality, or ‘handedness,'” Liu says. “Non-chiral cobalt oxide thin movies are commonly utilized in modern electronics.”
When the team injected pure spin aligned perpendicular to the fabric’s chiral axis, they noted that the spin didn’t travel through the fabric. Nevertheless, when the pure spin was aligned either parallel or anti-parallel to the chiral axis, its absorption, or ability to go through the fabric, improved by 3000%.
“Since spin can only go through these chiral materials in a single direction, this might enable us to design chiral gateways to be used in electronic devices,” Sun says. “And this work also challenges a few of what we thought we knew about chiral materials and spin, which is something we would like to explore further.”
The work appears in Science Advances and is supported by the Department of Energy under award numbers DE-SC0020992 and ER46430; the Air Force Office of Scientific Research, Multidisciplinary University Research Initiatives (MURI) Program under award numbers FA9550-23-1-0311and FA9550-23-1-0368; and the National Science Foundation under award numbers DMR 2011978 and NSF-ECCS 2246254.
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.