In the realm of energy and technology, understanding the intricate dance between an electron’s spin and its movement is crucial for developing next-generation devices. Researchers Kazuki Nakazawa, Henry F. Legg, Renato M. A. Dantas, Jelena Klinovaja, and Daniel Loss from the University of Basel in Switzerland have been exploring this very phenomenon. Their work, published in the journal Physical Review Letters, focuses on a quantum effect that could help us better understand and harness the spin-orbit interaction (SOI), a key player in future technologies.
The spin-orbit interaction is a fundamental quantum mechanical phenomenon where the spin of an electron, a tiny magnetic field that the electron carries, is coupled to its motion. This interaction is a vital ingredient in many proposed technologies, such as spintronics, which aim to use the spin of electrons to carry information, and topological quantum computing, which uses exotic quantum states for computation. However, measuring and understanding the strength and nature of SOI, especially in complex structures like heterostructures (where different materials are layered together), has been a significant challenge.
The researchers have turned their attention to a quantum effect known as the nonlinear Shubnikov-de Haas (NSdH) effect. This effect is a cousin of the well-known Shubnikov-de Haas (SdH) effect, which is an oscillatory variation in the resistivity of a material in a magnetic field at low temperatures. The NSdH effect, however, is a second-order effect, meaning it’s proportional to the square of the applied electric field. The key finding of this research is that, unlike its linear counterpart, the NSdH effect is highly sensitive to the spin textures that arise from SOI.
Spin textures are patterns of electron spins in a material, and they can vary depending on the type of SOI present. The researchers demonstrated that the phase and beating (a phenomenon where two oscillations interfere with each other) of NSdH oscillations in nonlinear conductivities can clearly distinguish between different types of SOI. As a practical example, they showed how NSdH can distinguish between the linear and cubic Rashba couplings that are expected in germanium heterostructures. The Rashba effect is a type of SOI that can be tuned by applying an electric field, making it particularly interesting for potential applications.
This research establishes the NSdH effect as a powerful and sensitive probe of SOI. It offers a new framework for characterizing materials relevant to topology, spintronics, and solid-state quantum information technologies. In the energy sector, understanding and controlling SOI could lead to more efficient and novel electronic devices, which in turn could reduce energy consumption and improve the performance of electronic systems. This work is a significant step forward in our quest to harness the power of electron spin for future technologies.
Source: Nakazawa, K., Legg, H. F., Dantas, R. M. A., Klinovaja, J., & Loss, D. (2023). Probing Fermi-surface spin-textures via the nonlinear Shubnikov-de Haas effect. Physical Review Letters.
This article is based on research available at arXiv.