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FRINATEK-Fri prosj.st. mat.,naturv.,tek

Heterostructure optimization and novel epitaxy yielding chalcogenide-oxide magnetic bilayers

Alternative title: Optimalisering av epitaksi og heterostrukturer for Kalkogenid-oksid magnetiske bilag

Awarded: NOK 8.0 mill.

The HONEYCOMB project aims to make new nano materials for the next-generation electronics. But why are honeycombs important for electronics? Honeycomb refers to the characteristic hexagonal pattern bees make of vax to store honey in. This pattern we can find in many materials, amongst them Van-der-Waals materials like graphene and functional ceramics used in memory applications. Many of the functional properties of these materials are directly related to the honeycomb structure. As material engineers we can use that to design new functionality in our materials. In today’s technology we use the interface between similar materials to design functionality, for example the conductivity in transistors or solar cells. At the interface between dissimilar materials, we can have emergent properties; i.e. properties that none of the materials have individually. To make that happen we need to make these materials such that they are not mixed, but still are affected by each other. In the project we use a method of fabrication called pulsed laser deposition, where we “paint” layer by layer of each material, and each layer is only a few atoms thick. The different materials are connected by having the same symmetry, the honeycomb structure. By combining Van-der-Waals materials, with unique transport properties, with magnetic ceramics, we can design completely new material properties that can be used in quantum computing. We can for example make magnetic topological insulators – a “wet” dream for new electronics. These materials conduct electricity just on the edges of the material, and this conductivity is lossless. That means that it doesn’t have any resistance, which means it doesn’t lose energy and can go forever! In addition, the conductivity is quantized which means we can use it in quantum computing, a concept that might revolutionize how computers work.

Quantum materials has in recent years emerged as a cross-discipline concept, taking functional materials to the next level in the hunt for low-power, ultracompact spintronics. Two major research fields have shaped the past decade: Emergent interfaces in complex oxide heterostructures and topological insulators in 2D van der Waals materials. Combining the two is predicted to make devices with emergent phenomena, however, the experimental realization of such heterostructures remains in its infancy due to challenging synthesis. There is a need for high-quality growth, ultra-sharp interfaces with strong electron connectivity. This young talent proposal by Ingrid Hallsteinsen aim to use the synthesis and interface engineering schemes for oxides on growing high-quality magnetic 2D materials that can be tuned and functionalized in a heterostructure. Her speciality is in growing (111)-oriented complex oxides, which have the same hexagonal honeycomb surface structure as van der Waals materials opening for a well-defined interface with possibilities of using the surface structure to tune functional properties. The project focuses on one model system, the topological insulator Bi2Te3 with possible induced magnetism, grown on top of (111)-oriented LaFeO3 a tunable antiferromagnetic oxide. Three major challenges will be addressed in this project: pulsed laser deposition of high-quality 2D materials, utilising a hexagonal complex oxide base to study interface connectivity and preserve topology, and investigating the magnetic exchange coupling across the van der Waals interface.The underlying hypothesis behind HONEYCOMB is 1) The hexagonal symmetry provide connectivity to the van der Waals material, enabling high-quality synthesis and 2) the tailoring of the spin axis in the oxides provide a platform to design magnetic properties in the van der Waals material. Coming together the project will demonstrate a magnetic topological insulator with emergent interface properties.

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FRINATEK-Fri prosj.st. mat.,naturv.,tek