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.
- BESSY II: Phosphorous chains – a 1D material with 1D electronic propertiesFor the first time, a team at BESSY II has succeeded in demonstrating the one-dimensional electronic properties of a material through a highly refined experimental process. The samples consisted of short chains of phosphorus atoms that self-organise at specific angles on a silver substrate. Through sophisticated analysis, the team was able to disentangle the contributions of these differently aligned chains. This revealed that the electronic properties of each chain are indeed one-dimensional. Calculations predict an exciting phase transition to be expected as soon as these chains are more closely packed. While material consisting of individual chains with longer distances is semiconducting, a very dense chain structure would be metallic.
- Did marine life in the palaeocene use a compass?Some ancient marine organisms produced mysterious magnetic particles of unusually large size, which can now be found as fossils in marine sediments. An international team has succeeded in mapping the magnetic domains on one of such ‘giant magnetofossils’ using a sophisticated method at the Diamond X-ray source. Their analysis shows that these particles could have allowed these organisms to sense tiny variations in both the direction and intensity of the Earth’s magnetic field, enabling them to geolocate themselves and navigate across the ocean. The method offers a powerful tool for magnetically testing whether putative biological iron oxide particles in Mars samples have a biogenic origin.
- What vibrating molecules might reveal about cell biologyInfrared vibrational spectroscopy at BESSY II can be used to create high-resolution maps of molecules inside live cells and cell organelles in native aqueous environment, according to a new study by a team from HZB and Humboldt University in Berlin. Nano-IR spectroscopy with s-SNOM at the IRIS beamline is now suitable for examining tiny biological samples in liquid medium in the nanometre range and generating infrared images of molecular vibrations with nanometre resolution. It is even possible to obtain 3D information. To test the method, the team grew fibroblasts on a highly transparent SiC membrane and examined them in vivo. This method will provide new insights into cell biology.