New research conducted at the University of Birmingham reveals a significant influence of the electronic structure of metals on their mechanical properties.
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This groundbreaking study, published in the journal Science on October 26th, 2023, provides experimental evidence for the first time that there is a direct link between the electronic and mechanical characteristics of a s. While this connection had been theoretically anticipated, it was previously believed to be too subtle to detect in an experimental setting.
Mechanical properties are typically described in terms of the bonding between atoms, while electronic properties of metals are described by states that extend across many atoms. The atomic lattice (the term used to describe the arrangement of atoms) of a metal and its mechanical properties are generally thought of as being unaffected by which electronic states are occupied and which are empty, but in this work, we show that this is not always a good assumption.
Dr. Clifford Hicks, Reader, Condensed Matter Physics, University of Birmingham
A collaborative team of researchers from the University of Birmingham and the Max Planck Institute for Chemical Physics of Solids in Dresden, Germany, conducted experiments using the superconducting metal strontium ruthenate (Sr2RuO4).
They examined lattice distortion in relation to applied stress and observed that when Sr2RuO4 is compressed by approximately 0.5%, Young's modulus, a measure of mechanical stiffness, decreases by around 10%.
Upon further compression, the material experiences an increase of approximately 20% in Young's modulus. This change corresponds to the occupation of a new set of electronic states, which was previously identified through electronic measurements but not mechanical ones.
Whilst it is completely standard to measure stress-strain relationships in mechanical engineering, it is not something that has been done to study electronic properties. This is because the metals that have interesting electronic properties tend to be brittle, making it hard to apply large forces. Also, large strains are typically required to meaningfully alter electronic properties. In this experiment, samples of Sr2RuO4 were compressed by up to 1%. To visualize that, imagine taking a metrestick made of granite, and squeezing it until it is 99 cm long.
Dr. Clifford Hicks, Reader, Condensed Matter Physics, University of Birmingham
To address these challenges, the researchers had to develop new instrumentation capable of measuring small and delicate samples while operating at cryogenic temperatures, as electronic measurements are more precise at lower temperatures. This endeavor required five years of planning and design.
This pioneering research, supported by funding from the German Research Foundation (Deutsche Forschungsgemeinschaft) and the Max Planck Society, marks a groundbreaking achievement in its unique approach.
With the successful completion of this experiment on one material, the researchers are eager to extend similar measurements to other metals. A version of the machine designed for this project is being produced by a UK-based engineering company, and as the apparatus continues to undergo development, it may find utility in the investigation of high-strength alloys.
This project serves as a testament to how curiosity-driven, fundamental research can pave the way for the development of new technologies with tangible, practical applications.
Journal Reference:
Noad, H. M. L., et al. (2023) Giant lattice softening at a Lifshitz transition in Sr2RuO4. Science. doi.org/10.1126/science.adf3348
Source: https://www.birmingham.ac.uk/index.aspx