Spin and topological effects in 2D quantum material devices

Doktorsavhandling, 2026

Topological quantum materials have unique properties in their so-called electronic band structures, which can be understood as hills and valleys in a landscape that electrons travel through. When electrons flow through these landscapes, both their movement and their magnetic spin properties are affected, which gives rise to unique physical phenomena.

Many of these materials are known as van der Waals materials and consist of thin layers stacked on top of each other, each one only a few atoms thick. This thesis explores how electrons behave when they move through such topological van der Waals quantum materials.

First, we design a useful spin sensing technique that is based on microscopic devices with graphene, which is a single layer of carbon atoms and is exceptional for carrying spins. This technique allows us to detect tiny magnetic patterns in ultrathin magnets without needing advanced microscope equipment.

Next, we study different topological quantum materials by combining them with graphene in similar devices. When we pass an electric current through the materials, the magnetic spins of the moving electrons line up in parallel. This so-called spin polarisation effect is observed at room temperature, and it can become essential for controlling magnetic memory and logic in future computing technologies.

Finally, we investigate how electrons behave when they flow through a magnetic topological quantum material. We see that the electrons move in an unusual manner which doesn’t follow the typical Ohm’s law. We also find that this strange electron movement can be used as a sensitive probe of the internal properties of the material, which can lead to new fundamental insights as well as novel technological applications.

Together, these results give a taste of the strange electronic landscapes in these fascinating materials, which can be a pathway towards both unexplored physics and new technological solutions.