Graphene Achieves 100% Spin-charge Interconversion Via Spin-pseudospin Entanglement Control, Enhancing Spintronics

Efficiently converting charge current into spin current is a key challenge in spintronics, and researchers are increasingly turning to graphene as a promising material for this purpose. Joaquín Medina Dueñas, Santiago Giménez de Castro, Jose H. Garcia, and Stephan Roche, all from the Institut Català de Nanociència i Nanotecnologia (ICN2), CSIC and BIST, now demonstrate a pathway to achieve 100% efficiency in this conversion process. The team reveals that by carefully controlling the interplay between spin and pseudospin, a property related to the electron’s wave-like behaviour, they can unlock a highly efficient spin-charge interconversion mechanism. Their work establishes that a combined spin-pseudospin operator remains conserved within graphene, enabling complete charge-to-spin conversion via the Rashba-Edelstein effect and also revealing a robust, disorder-resilient spin Hall effect, paving the way for novel and highly effective spintronic devices.

This work investigates the mechanisms governing spin-charge interconversion, focusing on controlling the entanglement between spin and pseudospin to maximize the efficiency of spin generation and detection. By manipulating the symmetry of the graphene lattice and applying tailored electric fields, scientists demonstrate the potential to enhance spin-orbit interaction and achieve optimal spin-charge interconversion efficiencies. The team explores how intrinsic and extrinsic spin-orbit mechanisms interact, revealing that the Rashba effect, arising from structural asymmetry, plays a crucial role in determining the spin polarization of generated carriers.

Through detailed calculations of the material’s electronic structure, the study establishes a link between graphene lattice symmetry and the efficiency of spin-charge interconversion. The results show that introducing specific edge terminations or applying external strain can significantly enhance Rashba spin-orbit coupling, substantially increasing the spin Hall angle. Furthermore, researchers demonstrate that combining the Rashba and intrinsic spin-orbit mechanisms allows tailoring the spin polarization of generated carriers, enabling the design of highly efficient spin filters and polarizers. These findings pave the way for novel spintronic devices based on graphene, with potential applications in low-power electronics, data storage, and quantum computing.

Graphene Heterostructures Enhance Charge-Spin Conversion Efficiency

This study investigates the efficiency of converting charge current into spin current in graphene-based materials, expanding on theoretical models with results from numerical simulations and addressing the robustness of the effect in the presence of material imperfections. The research focuses on graphene heterostructures, materials combining graphene with other substances to tune electronic properties and introduce new functionalities. Key concepts include charge-to-spin conversion, crucial for spintronic devices, and the spin Hall effect, where charge current generates a transverse spin current. The Rashba effect, arising from structural asymmetry, is also central to the research.

The supplementary information explores the impact of additional interactions on charge-to-spin conversion efficiency, including a staggered onsite potential and valley-Zeeman spin-orbit coupling. The results demonstrate that the efficiency remains robust even with these interactions, and detailed transport calculations confirm this resilience even in disordered systems with charge mobility comparable to that of real graphene samples. The study demonstrates the robustness of charge-to-spin conversion in graphene heterostructures against various perturbations, crucial for developing practical spintronic devices. The electronic properties of graphene heterostructures can be tuned by controlling interactions between materials, opening possibilities for designing materials with specific functionalities.

Efficient Spin-Charge Interconversion in Graphene

This research demonstrates a pathway to achieving fully efficient spin-charge interconversion in graphene, a crucial process for spintronic devices. Scientists successfully showed that by carefully controlling the interplay between spin and pseudospin degrees of freedom, it is possible to overcome limitations inherent in conventional systems. The key finding lies in the conservation of a combined spin-pseudospin operator, enabling a 100% efficient conversion via the Rashba-Edelstein effect, where an electric current generates a spin current. Furthermore, the team demonstrated the robustness of this effect in disordered systems, and identified a disorder-resilient spin Hall effect arising from the combined Rashba and Kane-Mele spin-orbit couplings. These results establish spin-pseudospin correlations as a powerful mechanism for tailoring spintronic devices and propose graphene as an ideal platform for maximizing spin-charge interconversion efficiency.