Researchers from NC State University and the University of Pittsburgh have studied the movement of spin information, known as a pure spin current, through chiral materials. Chiral materials are ones that cannot be superimposed on their mirror image, such as a left-handed glove and a right-handed glove. The researchers found that the direction in which spins are injected into these materials affects their ability to pass through them, with a 3000% improvement in absorption when the spin was aligned parallel or anti-parallel to the chiral axis. This discovery could lead to the design of energy-efficient spintronic devices for data storage, communication, and computing.
Spintronic devices utilize the spin of an electron instead of its charge to create current and transfer information through electronic devices. Moving spin information through a material without also moving the associated charge is a goal in spintronics, as moving charge requires more energy and leads to increased heat generation in electronic devices. By studying the behavior of spin in chiral materials, researchers can better control the direction of spin within the material, allowing for the development of more efficient spintronic devices.
It was previously believed that the chirality, or ‘handedness,’ of a material played a significant role in how spin would move through it. However, the researchers found that injecting pure spin into chiral materials resulted in absorption that strongly depended on the angle between the spin polarization and the chiral axis. This means that the alignment of spin polarization relative to the chiral axis determines the material’s ability to absorb and pass spin currents, challenging previous assumptions about the relationship between chirality and spin movement.
The researchers utilized two different approaches, microwave particle excitation and ultrafast laser heating, to inject pure spin into two chiral cobalt oxide thin films with different chirality. They observed that when the spin was aligned perpendicular to the material’s chiral axis, it did not travel through the material. However, alignment parallel or anti-parallel to the chiral axis resulted in a significant improvement in absorption, highlighting the importance of spin polarization direction in determining the material’s ability to pass spin currents.
By demonstrating the impact of spin alignment on the absorption of spin current in chiral materials, the researchers suggest that chiral gateways could be designed for use in electronic devices. This discovery opens up new possibilities for developing energy-efficient spintronic devices that can effectively transfer spin information through materials in a controlled manner. Further exploration of the relationship between chirality and spin movement is needed to fully understand the potential applications of chiral materials in spintronics.
The research, published in Science Advances, was supported by various funding sources including the Department of Energy, the Air Force Office of Scientific Research, and the National Science Foundation. The study involved researchers from NC State University and the University of Pittsburgh, with co-first authors including NC State postdoctoral researcher Rui Sun, NC State graduate student Ziqi Wang, and University of Pittsburgh Research Assistant Professor Brian Bloom. This collaboration between institutions has led to new insights into the behavior of spin in chiral materials and its implications for the design of future spintronic devices.
