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Spin transport and spin-orbit phenomena in 2D materials

Periodic Reporting for period 1 - 2DSTOP (Spin transport and spin-orbit phenomena in 2D materials)

Reporting period: 2019-03-01 to 2021-02-28

The great success of silicon-based microelectronics technology in the last century enabled the building of smarter and faster electronic devices such as mobile phones and computers. However, addressing the rising computing needs of our society combined with the resulting increasing ecological footprint requires continuous miniaturization of such devices, improving performance and lowering energy consumption. The scientific community nowadays is following two different paths to tackle these technological challenges. Firstly, new material systems with exotic properties such as two-dimensional (2D) materials like graphene were proposed to replace silicon. Secondly, new research fields such as spintronics with radically different device concepts are explored. The aim of 2DSTOP was to combine these two approaches and to study 2D materials-based spintronics.
Spintronics relies on the electrical control of magnetism or vice versa. A well-demonstrated application of spintronics is magnetic data storage which is an integral part of any electronic device, for example, the hard disk drives of our computers. For such applications, materials with efficient spin-to-charge current conversion are needed. The objective of the 2DSTOP project was to study spin transport and spin to charge current conversion in 2D materials such as graphene and transition metal dichalcogenides
Before the 2DSTOP project, the researcher provided the first unambiguous experimental demonstration of spin to charge conversion (SCC) due to spin Hall effect in graphene via spin-orbit proximity with transition metal dichalcogenides such as MoS2. Inspired by this result, the researcher planned to perform further investigation of spin phenomena in 2D materials. The researcher optimized the lateral spin-valve device to use for the spin transport and spin-to-charge conversion studies. Using this device, the researcher studied spin transport and spin to charge conversion in transition metal dichalcogenide MoTe2 and graphene combined with an insulator. The researcher also exploited the electrical tunability of spin current generation in graphene.
Through the weekly meetings between the researcher and the supervisor, the progress of the implementation of the project was analysed. Three articles in peer-reviewed journals, especially in high impact journal Nano Letters, were published during the project. Acknowledging the high-quality results, the researcher was invited to present his works at important conferences such as Americal Physical Society March meeting-2020 and IEEE Magnetism and Magnetic Material. Additionally, the results were further disseminated in Joint European Magnetic Society conference-2019 and also via online seminar series.
Graphene has been known as an excellent material for long-distance spin transport due to its weak spin-orbit coupling (SOC). However, the same reason makes graphene an adverse candidate for different spintronics applications in which strong SOC is required, such as spin-charge interconversions. Solving this long stood issue, the researcher observed for the first time the spin current generation phenomena such as the spin Hall effect in graphene. Later, a similar result was obtained in a different 2D material such as transition metal dichalcogenides. Due to large efficiency and electrical tunability, these 2D materials can be the building blocks of future high-density, multifunctional, and low power-consuming spintronics devices. This way, the results obtained during the 2DSTOP project contribute to the socio-economical growth of the society.
The graphene-based spin-to-charge conversion device optimized during the project became a formidable platform to study spin-orbit effects in a variety of 2D materials and their heterostructures. Using similar devices, many follow-up works studying spin-orbit effects in 2D materials have been reported in the literature. This way, 2DSTOP provided a high impact on the progress of the 2D spintronics research field
Schematic diagram of proximity induced spin Hall effect in graphene