A review on engineered van der Waals systems for (opto-)spintronic applications

by Virginia Greco

In a review just published in Nature Nanotechnology, the recent progress and enormous potential of van der Waals heterostructures are highlighted. These artificial materials, made up of layers of different 2D crystals, can be designed to exhibit specific functionalities to be harnessed in spintronic and opto-spintronic devices.

Bidimensional (2D) materials like the renowned graphene are atomic layered crystals which exhibit appealing physical properties that are not observed in their bulk counterparts. Extremely interesting for a large variety of applications, 2D materials can also be stacked together to form novel structures, which combine the characteristics of the single layers’ materials but also give rise to completely new properties. These van der Waals heterostructures (characterised by weak van-der-Waals forces between layers) can be conveniently engineered to design artificial materials on demand and with tailored made properties. In the case of spintronics, a research field that exploits the electron spin instead of its charge as a mean for information storage and communication, van der Waals systems offer a rich variety of potential device functionalities, which could be foundational for the advent of atomically-thin ultra-fast and low power electronics and next generation non-volatile memory technologies.

A review article published in Nature Nanotechnology presents the latest advances and future prospects in 2D spintronics and opto-spintronics (in which electrons’ spin is controlled through light) based on the use of the emerging vast family of van der Waals heterostructures. This work has been coordinated by ICREA Prof. Sergio O. Valenzuela, leader of the ICN2 Physics and Engineering of Nanodevices Group, and the first author of the paper is Dr Juan F. Sierra, Senior Researcher in Prof. Valenzuela’s group. The other authors of this work are ICREA Prof. Stephan Roche, leader of the ICN2 Theoretical and Computational Nanoscience Group , Prof. Jaroslav Fabian, from the University of Regensburg (Germany), and Prof. Roland Kawakami, from Ohio State University (US).

As a starting point, the article provides an overview of the current knowledge of spin dynamics in 2D materials and forefront research on spin injection, detection and manipulation. Various 2D materials are examined, including graphene, 2D magnets, semiconducting transition metal dichalcogenides and topological insulators. Then, the review moves on to a discussion on proximity-induced effects, by which it is possible to imprint properties from one layer onto another across their van der Waals interfaces. In particular, proximity induced spin-orbit coupling and magnetic exchange interaction provide unprecedented opportunities for designing efficient spintronic devices. Finally, current challenges and future lines of development in this vast field of research are presented.

The possibility to build multifunctional heterostructures by assembling different 2D crystals, obtaining novel artificial materials that host new physical phenomena, is a powerful tool with great potential applications, especially in spintronics, opto-spintronics and other related fields. New devices based on carefully engineered van der Waals heterostructures could be developed, such as memory elements, reconfigurable spin-logic circuits, spin-transistors, microwave nano-oscillators, flexible or wearable spintronic platforms, and so on. Progress in this research may also lead to revealing novel classes of artificial quantum materials and contribute to advances in information and quantum computing technologies.

Reference article:

Juan F. Sierra, Jaroslav Fabian, Roland K. Kawakami, Stephan Roche & Sergio O. Valenzuela, Van der Waals heterostructures for spintronics and opto-spintronics. Nature Nanotechnology (2021). DOI: 10.1038/s41565-021-00936-x