Ultrafast manipulation of magnetic order via charge transfer in van der Waals heterostructures

Charge transfer plays an essential role in fundamental chemical and biological processes such as photocatalysis and photosynthesis. This mechanism is also increasingly important in modern electric and optoelectronic devices that consist of semiconducting heterostructures, where the movement of charges across the interfaces between the constituent layers determines their overall effectiveness. Despite its significance, charge transfer remains largely unexploited in magnetic systems due to the challenge of finding materials that blend semiconducting and magnetic properties. Recently, the discovery of semiconducting van der Waals (vdW) materials that are magnetic down to single atomic layers has enabled the effective integration of semiconducting and magnetic properties along with reduced dimensionality. This project aims to investigate the lesser-known antiferromagnetic order, characterized by spins that align opposite to their neighbours, contrasting with traditional magnetic materials that depend on ferromagnets where neighbouring electron spins align parallel to establish ferromagnetic order. Antiferromagnetic alignment offers considerable advantages for memory technology, enabling magnetic bits to be packed more densely and operate at speeds typically a thousand times faster than those of ferromagnets. Additionally, the immunity of antiferromagnets to moderate external magnetic fields enhances memory application stability, although their detection challenges conventional methods. The proposed research is designed to demonstrate that charge transfer in antiferromagnetic vdW heterostructures facilitates ultrafast manipulation of magnetic order. Employing short laser pulses, time-resolved experiments will probe dynamic processes on femtosecond and picosecond scales. The focus will be on the effects of charge transfer across various vdW heterostructure combinations to enhance understanding of the interactions between key physical properties—electronic, optical, and magnetic. Specifically, the research will focus on the interaction between excitons (quasi-particles of bound electrons and holes), photons, and spins, aiming to incorporate quantum effects for ultrafast and energy-efficient electronic devices. Efforts will be concentrated on visualizing and manipulating antiferromagnetic spins in both space and time, striving to achieve rapid transitions between ferromagnetic and antiferromagnetic states, and exploring how these transitions affect excitonic properties. The envisioned ultrafast control of magnetic order through interfacial charge transfer holds significant promise for data storage and quantum technologies. By exploring the fundamental dynamic properties of the spin degree of freedom within a semiconducting environment, we can enhance the integration of magnetic compounds. Such advancements are crucial for achieving nonvolatility, faster data processing, reduced power consumption, and higher integration densities in future devices.