Unveiling finer details in the physics of materials

Scientists at the European XFEL’s SCS instrument routinely use a technique called transient X-ray absorption spectroscopy (XAS) to investigate materials that have applications in data storage and processing, catalysis, or in the search for room temperature superconductors. Investigating very small changes in the motion of electrons within a material’s structure on ultrashort timescales provides scientists with fingerprints of the complex processes at play within them. This helps them characterise samples that are important for energy and materials research.

Using the European XFEL’s brilliant pulses, researchers can overcome some of the issues of conventional transient XAS—such as long measurement times—but the varying intensity of European XFEL’s pulses provides its own challenges. Now, scientists at SCS have implemented a new sampling scheme for improving the efficiency of such measurements.

Read more on the European XFEL website

Image: The X-ray beam is split into three copies. Two of these copies are passed through identical samples of the material under investigation, with one of these samples also being illuminated by a laser (‘optical laser’ in the figure). This transforms it into a new state, interesting to researchers. From this, scientists are able to ‘subtract’ detrimental noise, revealing the finest details of the sample under investigation.

Magnetic sandwich mediating between two worlds

Scientists couple terahertz radiation with spin waves

An international research team led by the Helmholtz-Zentrum Dresden-Rossendorf (HZDR) has developed a new method for the efficient coupling of terahertz waves with waves of much shorter wavelengths, so-called spin waves. As the experts report in the journal Nature Physics (DOI:  10.1038/s41567-022-01908-1), their experiments, in combination with theoretical models, clarify the fundamental mechanisms of this process previously thought impossible. The results are an important step for the development of novel, energy-saving spin-based technologies for data processing.

“We were able to efficiently excite high-energy spin waves using terahertz light in a sandwich-like material system consisting of two metal films a few nanometers thick, with a ferromagnetic layer sandwiched in between,” says Dr. Sergey Kovalev of the Institute of Radiation Physics at HZDR, where the experiments were conducted. Electrons have an effective spin which behaves like a spinning top. And like a gyroscope, an external perturbation can tilt the spin’s axis of rotation: A gyroscopic motion, called precession, follows suit. In ferromagnetic materials, there is a very strong interaction between the electron spins, and as a result, a precession started locally continues in the form of a spin wave throughout the ferromagnetic material layer. This is interesting because a spin wave – like any wave – can be used as an information carrier.  While each electron spin is in motion, in the ferromagnets considered it remains in its position in the atomic lattice, therefore no current flow is involved. So, unlike in today’s computer chips, there are no heat losses due to currents in spin-based devices.

Read more on the HZDR website

Image: A terahertz light wave (from left) is converted into a spin wave (right) in a sample of thin metallic layers. In a heavy metal layer (left), electrical currents are first excited by the terahertz field. Within an ultrashort time, the spin Hall effect leads to the accumulation of spins with a certain orientation at the interface with a ferromagnetic layer (right). This directed spin current then triggers a coherent, nanomater-wavelength spin wave in the ferromagnetic material.

Credit: HZDR/Juniks

ExPaNDS webinar series to showcase achievements and look to the future

We’re pleased to announce our upcoming topic-based webinars which will take place during the coming month before the end of our grant in February 2023. The webinar topics have been selected with the help of our work package leaders and some of the highlighted use cases taken directly from the PaN community throughout our grant.

The series will provide a great opportunity to showcase some of the outcomes of our grant to the PaN facility user communities. We will present some key findings from the recently conducted data consultation, which was sent to over 14,000 PaN facility users.

The ongoing work of ExPaNDS has been very important to the PaN community and we have invited senior community figures to discuss the future needs and requirements for their respective discipline or technique to keep the momentum going beyond the grant.

We will have flash talks from our work packages with focus being on FAIR, data catalogue services, data analysis and an overview of the PaN training platform.

Read more on the ExPaNDS website

Image: Chairman of the DESY Board of Directors – Professor Dr Helmut Dosch

Brilliant people working towards a common goal

It’s #LoveYourDataWeek so it’s fitting that this week’s #LightSourceSelfie features a data expert. Mathew Cherukara leads the Computational X-ray Science Group at the Advanced Photon Source (APS) at Argonne National Laboratory near Chicago.

Mathew, who is from Kerala in India, works with his colleagues to develop the computational tools, algorithms and machine learning models used to analyse data from the beamlines at the APS. The first time Mathew saw a light source he recalls, “I couldn’t believe that science on this scale was being done every single day”. Mathew also talks about the fact that, after the APS upgrade, the data rates and computational needs will increase 100 to 1,000 times. For Mathew, the best thing about working at a light source is all the brilliant people working towards a common goal. When Mathew isn’t working, he enjoys taking long walks with his dog and we’re treated to a very cute dog moment at the end of the video #LoveYourDog!

APS #LightSourceSelfie

Understanding the physics in new metals

Researchers from the Paul Scherrer Institute PSI and the Brookhaven National Laboratory (BNL), working in an international team, have developed a new method for complex X-ray studies that will aid in better understanding so-called correlated metals. These materials could prove useful for practical applications in areas such as superconductivity, data processing, and quantum computers. Today the researchers present their work in the journal Physical Review X.

In substances such as silicon or aluminium, the mutual repulsion of electrons hardly affects the material properties. Not so with so-called correlated materials, in which the electrons interact strongly with one another. The movement of one electron in a correlated material leads to a complex and coordinated reaction of the other electrons. It is precisely such coupled processes that make these correlated materials so promising for practical applications, and at the same time so complicated to understand.

Strongly correlated materials are candidates for novel high-temperature superconductors, which can conduct electricity without loss and which are used in medicine, for example, in magnetic resonance imaging. They also could be used to build electronic components, or even quantum computers, with which data can be more efficiently processed and stored.

Read more on the BNL website

Image: Brookhaven Lab Scientist Jonathan Pelliciari now works as a beamline scientist at the National Synchrotron Light Source II (NSLS-II), where he continues to use inelastic resonant x-ray scattering to study quantum materials such as correlated metals.

Credit: Jonathan Pelliciari/BNL