New instrument at BESSY II commences user operation
The Russian-German Laboratory operating its own beamline at BESSY II. © HZB/Michael Setzpfandt
The new measurement station will be available beginning at the next beamtime period. © HZB/Michael Setzpfandt
A new instrument became available to the users of BESSY II on Oct. 28, 2019. The new beamline and apparatus for spin- and angular-resolved photoemission in the Russian-German Laboratory at BESSY II have successfully completed their test phase. They facilitate precise measurements of the electron band structure and spin of different material classes such as topological insulators and magnetic sandwich structures, as well as novel perovskite-based solar-cell materials. A photoelectron microscope has also been developed which is particularly important for nanoscopic structures.
The Russian-German Laboratory has existed at BESSY II for more than fifteen years, operating its own beamline for absorption and photoelectron spectroscopy. Now, in addition to the dipole beamline, lab members have also set up a powerful measurement station for spin- and angularly-resolved photoelectron spectroscopy and photoelectron microscopy on an undulator beamline. This measurement station was developed together with Technische Universität Dresden (TU Dresden) and Freie Universität Berlin through a German Federal Ministry of Education and Research (BMBF) grant. The measurement station along with Russian and German user-support teams will be available beginning at the next beamtime period.
International Workshop
Prof. Eckart Rühl of Freie Universität Berlin, chairman of the laboratory's steering committee, emphasises the strong ties with Russian colleagues. “In order to familiarise Russian research groups with the new opportunities offered by the instrument, we have launched the instrument as part of an international workshop”, explains Rühl. 26 researchers (seven women and nineteen men) from Russia, Germany, Spain, and Japan will report on their experiments over the two-day event.
Measuring spin-orbit interactions
“In recent years, spin-orbit interactions, i.e. the coupling of magnetic orientation to the direction of motion of electrons, has developed without pause to become a main research topic in solid-state physics. This was particularly due to the discovery of a new class of materials called topological insulators, which was honoured by the 2016 Nobel Prize in Physics“, explains Prof. Oliver Rader of the HZB, in whose department the new instrument is located. “This led to a sharp increase in international demand for experiments that can detect spin directly.” The current interest in stable two-dimensional solids might also contribute to this demand as well, for novel two-dimensional magnets such as CrI3 have been discovered in recent years.
Reception at the Russian Embassy
The great importance attached to the laboratory was exemplified by the participation of the Embassy of the Russian Federation: Alexander Rusinov, attaché for the Department of Education, Science, and Technology at the Embassy, gave the opening address, and the Federation Ambassador received the participants in the evening.
Partners of the collaboration:
The collaboration is being supported by Freie Universität Berlin, TU Dresden, TU Freiberg, and the Helmholtz-Zentrum Berlin on the German side, while from the Russian side by St. Petersburg State Univerisity, the Kurchatov Institute (Moscow), Ioffe Physical-Technical Institute of the Russian Academy of Sciences (Ioffe Institute, St. Petersburg), and the Shubnikov Institute of Crystallography (Moscow).
- Green hydrogen: A cage structured material transforms into a performant catalystClathrates are characterised by a complex cage structure that provides space for guest ions too. Now, for the first time, a team has investigated the suitability of clathrates as catalysts for electrolytic hydrogen production with impressive results: the clathrate sample was even more efficient and robust than currently used nickel-based catalysts. They also found a reason for this enhanced performance. Measurements at BESSY II showed that the clathrates undergo structural changes during the catalytic reaction: the three-dimensional cage structure decays into ultra-thin nanosheets that allow maximum contact with active catalytic centres. The study has been published in the journal ‘Angewandte Chemie’.
- An elegant method for the detection of single spins using photovoltageDiamonds with certain optically active defects can be used as highly sensitive sensors or qubits for quantum computers, where the quantum information is stored in the electron spin state of these colour centres. However, the spin states have to be read out optically, which is often experimentally complex. Now, a team at HZB has developed an elegant method using a photo voltage to detect the individual and local spin states of these defects. This could lead to a much more compact design of quantum sensors.
- Solar cells on moon glass for a future base on the moonFuture settlements on the moon will need energy, which could be supplied by photovoltaics. However, launching material into space is expensive – transporting one kilogram to the moon costs one million euros. But there are also resources on the moon that can be used. A research team led by Dr. Felix Lang of the University of Potsdam and Dr. Stefan Linke of the Technical University of Berlin have now produced the required glass from ‘moon dust’ (regolith) and coated it with perovskite. This could save up to 99 percent of the weight needed to produce PV modules on the moon. The team tested the radiation tolerance of the solar cells at the proton accelerator of the HZB.