Research Area
With the discovery of graphene in 2004, the wonderland of low-dimensional systems opened up to experimental physicists allowing them to verify exotic theories and discover various novel phenomena that arises when dimensionality of a system is reduced from 3d to 2d/quasi-2d limit. Graphene and all other graphene-like vdW materials that enriches this new platform, often shares fascinating characteristics like enhanced transport and optical properties, spin dynamics, quantum correlation, etc. Being coupled together with the weak out of the plane van der Waals force, individual layers can be easily peeled off these materials to study and analyze artifacts of physical laws and interactions in lower dimensions. Moreover, coupling these monolayers of vdW materials with each other while tuning parameters like angle between them, often leads to emergent phases like magic angle superconductivity, van Hove singularity etc. Stacking monolayers of different vdW materials, hetero-structures and ultra-thin devices can be engineered, making it accessible to test for optimal functionality by fine tuning the key parameters.
Q. Shao et al., IEEE Transactions on Magnetics, vol. 57, no. 7, July 2021
Hall bar patterned on a few layer vdW ferromagnet
Among all the alluring criteria those appears in these vdW systems, one of the most practically useful and potentially game-changing one is ferromagnetism, especially when it retains in monolayer and room temperature limit. Although, compared to other behaviors, 2d ferromagnetism is hard to find at room temperature, as Mermin-Wagner theorem says, due to insufficient exchange strength and enhanced thermal fluctuation. But, by enhancing the exchange interaction by stacking atomically thin layers of a vdW material, introducing anisotropic interaction or using voltage-controlled gate-tunable devices, ferromagnetic long-range order can be stabilized in few qausi-2d systems. If a 2d ferromagnet with high critical temperature, high conductivity, and large magnetization, can be synthesized and made into reality, it will be a major boost in the field of spintronics .
My objective of research is preparing and studying room temperature vdW 2D ferromagnetic systems with enhanced spin-spin exchange interaction. With the help of various measurement techniques like SQUID magnetometer, PPMS(physical property measurement system), PhaseFMR, ST-FMR etc. static and dynamical spin properties like phase transition, ferromagnetic resonance, anisotropic magneto-resistance, anomalous Hall effect, inverse spin Hall effect etc can be analyzed. With the help of a spin pumping mechanism, we can measure the efficiency of spin transport in a heterostructure when these systems are integrated into a device as spin sources. There are also other scopes to study the emergent properties of the system by fabricating ultrathin devices by exfoliating vdW materials towards monolayer limit. Various architectures like magnetic tunnel junction (MTJs) and spin-valves are recently being studied in this direction, which can bring revolution in the field of magnetic memory and data storage.
Nano Lett. 2019, 19, 6, 3993–3998