New road towards spin-polarised currents

Hafniumdiselenide is a quasi twodimensional material with interesting properties for spintronics. Here, its crystal structure is shown.

Hafniumdiselenide is a quasi twodimensional material with interesting properties for spintronics. Here, its crystal structure is shown. © O. Clark/HZB

The transition metal dichalcogenide (TMD) series are a family of promising candidate materials for spintronics. A study at lightsource BESSY II has unveiled that in one of those materials even simple linear polarised light is sufficient to selectively manipulate spins of different orientations. This result provides an entirely new route for the generation of spin-polarised currents and is a milestone for the development of spintronic and opto-spintronic devices.

The second half of the 20th century was the age of electronics, electronic devices became miniaturised and even more complex, creating problems by their energy consumption and waste heat. Spintronics promises to store or transport information based on spins alone, which would work faster with much less energy. Unfortunately it is still a challenge to control spin in a material by external fields reliably and at scale.

Quasi 2D-materials in the focus

The transition metal dichalcogenide (TMD) series are the most intensely studied quasi two-dimensional materials beyond graphene, with charge density waves, superconductivity and non-trivial topological all commonplace across the material family. Hafnium diselenide (HfSe2) belongs to this class of materials. Now scientists at BESSY II have unveiled a new property of its electronic structure that could lead to a more convenient route to generate and control spin currents.

“In order to shift from electronics to spintronics, we have to find materials wherein spin up and spin down electrons behave differently”, first author Oliver Clark explains. There are two ways to do this, he points out: “We can either externally perturb the material so that electrons of different spins become functionally inequivalent, or we can use magnets where the electrons of opposite spins are functionally different intrinsically.” For the first method, the difficulty lies in finding suitable pairings of materials and mechanisms by which spin control can be externally imposed. For example, in the so-called 2H structured TMDs, one needs perfect single crystals and a circularly polarised light source. By contrast, the second method is much easier, but integrating magnets into devices is problematic for the operation of conventional electronic components, especially on small scales.

Linearly polarised light does do the trick

But between those two ways, a middle ground exists, at least for some select materials such as HfSe2:“If you probe this material with linearly-polarised light – which is easier to produce than circularly polarised light - the material acts as a magnet in terms of its spin-structure. So the spin-selectivity becomes very easy, but you do not have the problems associated with other magnetic properties”, Clark explains. The advantage: Crystal quality or orientation of the sample no longer matter.

This provides an entirely new route towards the generation of spin-polarised currents from transition metal dichalcogenides. The physicists are very excited about the implications of this work: “Our results are of relevance not only to physicists concerned with layered two-dimensional materials, but as well to specialists in spintronic and opto-spintronic device fabrication”, Clark hopes.

arö

  • Copy link

You might also be interested in

  • Sodium-ion batteries: New storage mechanism for cathode materials
    Science Highlight
    18.07.2025
    Sodium-ion batteries: New storage mechanism for cathode materials
    Li-ion and Na-ion batteries operate through a process called intercalation, where ions are stored and exchanged between two chemically different electrodes. In contrast, co-intercalation, a process in which both ions and solvent molecules are stored simultaneously, has traditionally been considered undesirable due to its tendency to cause rapid battery failure. Against this traditional view, an international research team led by Philipp Adelhelm has now demonstrated that co-intercalation can be a reversible and fast process for cathode materials in Na-ion batteries. The approach of jointly storing ions and solvents in cathode materials provides a new handle for the designing batteries with high efficiency and fast charging capabilities. The results are published in Nature Materials.
  • Helmholtz Doctoral Award for Hanna Trzesniowski
    News
    09.07.2025
    Helmholtz Doctoral Award for Hanna Trzesniowski
    During her doctoral studies at the Helmholtz Centre Berlin, Hanna Trzesniowski conducted research on nickel-based electrocatalysts for water splitting. Her work contributes to a deeper understanding of alkaline water electrolysis and paves the way for the development of more efficient and stable catalysts. On 8 July 2025, she received the Helmholtz Doctoral Prize, which honours the best and most original doctoral theses in the Helmholtz Association.

  • Hydrogen storage in MXene: It all depends on diffusion processes
    Science Highlight
    23.06.2025
    Hydrogen storage in MXene: It all depends on diffusion processes
    Two-dimensional (2D) materials such as MXene are of great interest for hydrogen storage. An expert from HZB has investigated the diffusion of hydrogen in MXene using density functional theory. This modelling provides valuable insights into the key diffusion mechanisms and hydrogen's interaction with Ti₃C₂ MXene, offering a solid foundation for further experimental research.