Nonlinear spintronics
Abstract
<p indent="0mm">Nonlinear spintronics represents an emerging field that combines nonlinear dynamics with spintronics, offering new pathways beyond traditional spin-related effects. Traditional spintronics primarily focuses on the linear response of spin to external stimuli, such as electric fields and temperature gradients. However, nonlinear responses can persist even when linear responses are symmetry-forbidden, offering new opportunities for spintronics development. This article summarizes recent progress in nonlinear spintronics, focusing on several typical nonlinear spin transport phenomena, their physical mechanisms, experimental characterizations, and applications in spintronic devices. We emphasize the importance of these effects and aim to stimulate new research directions. The review begins by discussing the generation and manipulation of spin currents, which are crucial for spintronic devices. It highlights the nonlinear spin Hall effect, where the spin current is proportional to the square of the electric field, contrasting with the linear response in traditional spintronics. The article also covers the nonlinear spin Edelstein effect, where spin polarization is induced by the square of the electric current, and the nonlinear spin Nernst/Seebeck effect, where a temperature gradient drives the generation of nonlinear spin currents. Experimental observations of these effects are still scarce, but theoretical predictions suggest that they can be significant in various materials, including topological insulators and magnetic materials. The review also discusses the role of symmetry in allowing or prohibiting these nonlinear spin responses, providing a framework for predicting materials where these effects might be observed. Furthermore, the article explores the potential of nonlinear spin currents for device applications, such as spin memory devices and logic devices, and their potential for energy conversion and waste heat recovery. It concludes by highlighting the need for further experimental research to validate theoretical predictions and the development of new detection techniques to measure these subtle nonlinear effects. Nonlinear spintronics is a rapidly evolving field with the potential to significantly impact spintronic device performance and functionality. As research in this area progresses, it is expected to unveil new physics and practical applications, further expanding the capabilities of spintronics.</p>
