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Magnon propagation in two dimensional magnets

Periodic Reporting for period 1 - MptDM (Magnon propagation in two dimensional magnets)

Reporting period: 2021-06-01 to 2023-05-31

The most famous van-der Waal (vdW) material is monolayer graphene (Nobel Prize in Physics, 2004) which is often associated with extraordinary electronic properties, such as extremely high mobility and magnetoresistance. Such extraordinary electronic properties propel these materials as one of the most promising for beyond Si electronic technologies. From the scientific perspective, even after a decade of exploration, there are many things unknown in vDW materials- for eg, the mechanism of scattering at the charge neutrality point. During this project, two major research directions were carried out - (i) investigation of quantum linear magnetoresistance in vdW systems (ii) investigation of high-temperature quantum oscillations in vdW heterostructures. The first direction led to submission in Nature journal with the fellow as the co-lead author, which has been recently accepted for publication (Feb 2023). The second direction is currently being prepared for submission to a high impact journal (IF >20). The fellow is planning to disseminate these research outputs through invited talks in Singapore and India in 2023. The outcome of giant magnetoresistance (>100% at 0.1T) at room temperature using vdW materials from the first project direction may have a broad societal impact in the near future for integration of vdW materials in magnetic sensors. From a pure fundamental science impact, our work will inspire the search of Planckian scattering in other material systems particularly semi-metals that show linear magnetoresistance.
The project was run for four different work packages which are- (i)synthesis and characterization of 2D vdW materials, (ii) Fabrication of vdW devices, (iii) Measurement set-up, characterization and data analysis (iv)Dissemination and communication. Two major research results were achieve - (i) Origin of high temperature linear magnetoresistance in vdW systems (ii) Record magnetoresistance and mobility at room temperature of any material (ii) Discovery of high-temperature quantum oscillations in at the charge-neutrality point in vdW superlattices.

The work during the fellowship will produce two publications from the fellowship namely—
(1) Na Xin+, James Lourembam+, P. Kumaravadivel+, et al. ,“Strange magnetoresistance of high-mobility Dirac plasma”. Nature (Accepted Feb 2023) +equal contribution,
(2) James Lourembam, , “Hidden bloch states near neutrality point in graphene superlattices revealed by proximity screening” (Target submission to Science, end of 2023)
The DOI of the publications would be shared once they are generated by the publisher. In addition, the fellow interacted with faculty from University of New South Wales, Australia and Nanyang Technology University, Singapore about the outcomes and the fellowship. The fellow is currently in discussion to give talks in the following universities –(i) Nanyang Technology University, Singapore and (ii) City University of Hong Kong
At the University of Manchester, the fellow was responsible for furthering the research domain of physics at the neutrality point of graphene and graphene-based heterostructures. Notably the three highlights discovered at the neutrality point are –(i) Giant linear magnetoresistance at Dirac plasma (ii) Brown-Zak oscillations in screened vdW devices (iii) Coulomb drag of electrons and holes at Dirac Plasma. The first two discoveries are related to Planckian scattering, a phenomena closely related to strange metals and previously only studied in the context of High Tc superconductors. This universality of Planckian scattering across different unrelated material systems is completely new to the 2D community.
From the technological point of view, the discovery of giant magnetoresistance upto ~13,000 % in ambient conditions will likely generate a lot of industry interest particularly in the development of new types of magnetic sensors.