Lars Sjöström, Avdelningen för kvantkomponentfysik

Abstract: 

Two-dimensional (2D) quantum materials have attracted significant attention in recent years, both in the field of spintronics and in condensed matter physics. These materials feature unique electronic band structures that provide a rich platform for exotic topological quantum effects, which can be utilized both for the understanding of novel physical phenomena and for next-generation spintronic and quantum technologies.
Here, we investigate such exotic topological and spintronic effects in different types of 2D quantum materials through electrical, spin and magnetotransport measurements. First, we demonstrate nonlinear transport in the magnetic topological insulator MnBi2Te4, including an oscillatory odd/even behavior with higher harmonic orders [1]. This indicates exotic phases in the quantum geometry, such as a large quantum metric or Berry curvature multipoles. Second, we detect robust charge-spin interconversion in the topological insulator Bi1.5Sb0.5Te1.7Se1.3 [2] and the Weyl semimetal TaIrTe4 [3] using lateral graphene spin-valve devices. This shows the possibility of probing spin textures of topological quantum materials and making all-electrical room-temperature spintronic devices. Finally, we developed a technique for the electrical detection of different magnetic domain patterns through pure spin transport in graphene spintronic devices [4], which can pave the way for pure spin read-out of magnetic states in innovative memory and logic devices.
These findings provide a better physical understanding of 2D quantum materials and open routes towards their utilization in fast and energy-efficient next-generation spintronic and quantum technologies such as memory, logic and neuromorphic computing.

[1] Sjöström, L. et al. “Even/odd harmonic oscillations in magnetic topological insulator MnBi2Te4”, under preparation
[2] Hoque, M.A., Sjöström, L. et al. “Room temperature nonlocal detection of charge-spin interconversion in a topological insulator” (2024) npj 2D Materials and Applications, 8:10 https://doi.org/10.1038/s41699-024-00447-y
[3] Sjöström, L. et al. “Detection of charge-spin interconversion in the topological Weyl semimetal TaIrTe4”, unpublished
[4] Sjöström, L. et al. “Electrical detection of magnetic spin textures using pure spin currents in graphene”, under preparation

Huvudhandlare: Professor Saroj Prasad Dash

Examinator: Professor Tomas Löfwander

Biträdande handledare: Senior researcher Alexei Kalaboukhov

Diskussionsledare: Martina Ahlberg, Researcher, University of Gothenburg