Magnon propagation in two dimensional magnets
Two-dimensional (2D) materials, are crystalline planar structures with weak out-of-plane van der Waals (vdW) forces. Such 2D materials are often associated with extraordinary electronic, optical, and thermoelectric properties, such as extremely high mobilities. Ever since the isolation of graphene, the first 2D material, by Novoselov and Geim in 2004, the family of 2D materials have expanded by hundreds. However, long-range ferromagnetic order is typically not sustainable in 2D due to enhanced fluctuations. Consequently, 2D vdW magnets was only realized as late as 2017. Hence, it was only recently feasible to conduct elusive experiments for exploration of ground states, fundamental excitations and propagation of spin waves. Magnons, which are a quanta of spin waves, are particularly interesting to investigate in these 2D vdW magnets. In 2D, they exhibit step-like function of density-of-states as opposed to a gradually increasing function in three dimensional magnets. Meanwhile, other remarkable discoveries in these 2D vdW magnets such as a giant tunneling magnetoresistance has also been reported to be in close relation with magnon physics. The proposal aims to pursue seminal work in magnon excitation and propagation in 2D vdW magnets and leverage the outcomes to preposition next-generation of electron devices. So far, no report exists in quantifying magnon propagation length in a true 2D material (one or a few monolayers). On the technological front, using magnons instead of electrons to carry information in electronic devices would provide a significant low-power alternative to the existing technologies. The other highlight of this proposed device is the use of electrical signal for both injection and detection, allowing easier integration with electronics components. Driven by these exciting scientific and technological objectives, the project aims to overcome multidisciplinary challenges in physics, instrumentation, material science and device design .