How to use light to manipulate the spin in topological insulators
The picture shows the characteristic spin texture (arrows) in a topological insulator and how it is manipulated by circularly polarized light. © Rader/Sachez-Barriga/HZB
Researchers at HZB investigated the topological insulator bismuth selenide (Bi2Se3) by spin-resolved photoelectron spectroscopy at BESSY II. They found an astonishing difference depending on whether it is illuminated by circularly polarized light in the vacuum ultraviolet (50 electron volts, eV) and in the ultraviolet spectral range (6 eV). This result could help explaining how spin currents can be generated in topological insulators.
In the former case, the emitted electrons display the characteristic spin texture of topological insulators, which is aligned on a circle in the surface plane, similarly to a roundabout road sign. In the latter case, however, the spins do not only rotate completely out of this plane but also take on the spin direction imposed by the right or left circularly polarized light.
HZB researchers expect that this manipulation of the electron spin by light and the insight into its preconditions will be most useful for the generation of lossless spin currents in topological insulators.
Topological insulators are a novel state of matter with an insulating bulk and a metallic surface, which are interesting candidates for novel devices in future information technologies. Light-induced spin manipulation is one of the processes involved.The present work reveals the conditions for the generation of dissipationless spin currents in topological insulators.
Their results have just been accepted for publication in Physical Review X, the new top journal of the Americal Physical Society.
- Lithium-sulphur pouch cells investigated at BESSY IIA team from HZB and the Fraunhofer Institute for Material and Beam Technology (IWS) in Dresden has gained new insights into lithium-sulphur pouch cells at the BAMline of BESSY II. Supplemented by analyses in the HZB imaging laboratory and further measurements, a new picture emerges of processes that limit the performance and lifespan of this industrially relevant battery type. The study has been published in the prestigious journal Advanced Energy Materials.
- Largest magnetic anisotropy of a molecule measured at BESSY IIAt the Berlin synchrotron radiation source BESSY II, the largest magnetic anisotropy of a single molecule ever measured experimentally has been determined. The larger this anisotropy is, the better a molecule is suited as a molecular nanomagnet. Such nanomagnets have a wide range of potential applications, for example, in energy-efficient data storage. Researchers from the Max Planck Institute for Kohlenforschung (MPI KOFO), the Joint Lab EPR4Energy of the Max Planck Institute for Chemical Energy Conversion (MPI CEC) and the Helmholtz-Zentrum Berlin were involved in the study.
- Ernst Eckhard Koch Prize and Synchrotron Radiation Innovation AwardThis year, the Friends of Helmholtz-Zentrum Berlin (Freundeskreis des HZB e. V.) awarded the Ernst Eckhard Koch Prize to Dr. Dieter Skroblin of the Technische Universität Berlin for his outstanding doctoral thesis. The European Innovation Award Synchrotron Radiation went to Dr. Manfred Faubel from the Max Planck Institute for Dynamics and Self-Organization in Göttingen and Dr. Bernd Winter from the Fritz Haber Institute in Berlin. The award ceremony took place at this year's HZB user meeting.