Humboldt Fellow Alexander Gray comes to HZB
Alexander Gray (here in his lab at Temple University, Philadelphia, USA) will strengthen his collaboration with the team of Florian Kronast at BESSY II. © Privat
Alexander Gray from Temple University in Philadelphia, USA, is working with HZB physicist Florian Kronast to investigate novel 2D quantum materials at BESSY II. With the fellowship from the Alexander von Humboldt Foundation, he can now deepen this cooperation. At BESSY II, he wants to further develop depth-resolved X-ray microscopic and spectroscopic methods in order to investigate 2D quantum materials and devices for new information technologies even more thoroughly.
Topological insulators and Weyl semimetals are among the most exciting classes of materials for quantum devices. They are characterised by the fact that they have different electronic and magnetic properties at the surfaces and interfaces than in the volume.
Alexander Gray is a well-known expert in this field and frequently comes to BESSY II for short measurement periods, where he cooperates with Florian Kronast. As a Fellow of the Alexander von Humboldt Foundation, the American physicist can now finance regular guest stays at HZB with Florian Kronast's team and at Forschungszentrum Jülich with Claus Schneider's team. "The Humboldt Fellowship gives us more time, so we can investigate and discuss in more detail how the interplay between surface, interface and bulk properties in quantum materials leads to novel phenomena that enable device applications," he says.
Gray leads a team at Temple University in Philadelphia and also plans to send his students to BESSY II. "We want to develop new techniques to study the electronic and magnetic properties of 2D quantum materials and quantum devices in more detail," he outlines his goals. At BESSY II, Gray will primarily develop depth-resolved standing-wave photoemission microscopy further for this purpose. Kronast, Gray, and his former doctoral advisor Chuck Fadley have already combined this method with excitation by standing X-ray waves to enable depth resolution (SW-PEEM).
From mid-August, Alexander Gray is planning his first stay at BESSY II. He is not only looking forward to the measurements and many discussions, but also to the typical Berlin atmosphere: "The people are really open and friendly, and I have never experienced the famous "Berlin snout". I think if I do one day, I might deserve it." With this attitude, full of humor, his stay in Berlin will be a huge success in every aspect.
- Ultrafast dissociation of molecules studied at BESSY IIFor the first time, an international team has tracked at BESSY II how heavy molecules – in this case bromochloromethane – disintegrate into smaller fragments when they absorb X-ray light. Using a newly developed analytical method, they were able to visualise the ultrafast dynamics of this process. In this process, the X-ray photons trigger a "molecular catapult effect": light atomic groups are ejected first, similar to projectiles fired from a catapult, while the heavier atoms - bromine and chlorine - separate more slowly.
- Protons against cancer: New research beamline for innovative radiotherapiesTogether with the University of the Bundeswehr Munich, the HZB has set up a new beamline for preclinical research. It will enable experiments on biological samples on innovative radiation therapies with protons.
- Battery research with the HZB X-ray microscopeNew cathode materials are being developed to further increase the capacity of lithium batteries. Multilayer lithium-rich transition metal oxides (LRTMOs) offer particularly high energy density. However, their capacity decreases with each charging cycle due to structural and chemical changes. Using X-ray methods at BESSY II, teams from several Chinese research institutions have now investigated these changes for the first time with highest precision: at the unique X-ray microscope, they were able to observe morphological and structural developments on the nanometre scale and also clarify chemical changes.