Physics

Can precious metals become superconductors?

Predicted dependence of the superconducting critical temperature of ultrathin gold films as a function of film thickness. As the film thickness decreases, the temperature at which gold becomes superconducting can be measured experimentally and matches the temperature of well-known superconducting elements such as aluminum. Credit: A. Zaccone and G. Ummarino

Superconductivity is a phenomenon in which current flows through metals without resistance at sufficiently low temperatures. Certain metals are good superconductors, while others cannot superconduct at all.

Understanding what causes metals to become superconducting remains an open problem in fundamental condensed matter physics. Additionally, superconductivity in simple solid bodies is of great importance for technological applications. Consider that elemental aluminum is widely used in superconducting Josephson junctions used in quantum computing (e.g., qubit implementations).

For these reasons, an important field of research in recent decades has been devoted to finding new elements that have the potential to become superconducting under certain conditions.

This paper, published in Physical Review Materials, proposes a completely new approach to the search for new elements that can become superconductors.

For the past few years, I have been working on a new approach to quantitatively determine how thin film thickness affects the electronic properties of very thin metal slabs. The key principle is that only electron waves with wavelengths that do not exceed the size of the sample along a particular propagation direction are allowed to exist in a thin slab.

Obviously, along the direction perpendicular to the slab surface, the maximum allowed wavelength is about the thickness of the film, but in the vertical plane the electron wave can propagate at any wavelength.

The first implementation of this quantum confinement model with my former student Riccardo Travarino yielded promising results for ultrathin films of lead compared with experimental data from the literature.

However, this calculation is based on the Bardeen-Cooper-Schriefer theory of superconductivity, which is insufficiently accurate when the coupling between electrons and phonons in the lattice is strong, making it difficult to calculate the phonon spectrum in a realistic way. It is not taken into consideration.

Then I started collaborating with my Turin colleague Giovanni Ummarino. He is an expert on the Eliashberg theory of more sophisticated and realistic superconductivity theories, and deals with all the above points in an accurate and completely quantitative way, without the need for tunable parameters. can.

Using the most sophisticated version of Eliashberg’s superconductivity theory, combined with ab initio simulations and modern quantum confinement models for quasi-2D materials, ultrathin films of precious metals with thicknesses below 20 predicted that it would become superconducting when cast in 1nm.

This theory is completely quantitative and has no adjustable parameters. The most shocking prediction is that ultrathin gold (Au) films about 0.5 nanometers thick will become superconducting at a critical superconducting temperature equal to 1.1 Kelvin. This is essentially the same critical temperature of aluminum (Al), the material most commonly used for Josephson junctions implemented in quantum computer qubits.

This prediction could open new ways to realize ultrathin superconducting films of precious metals, which can combine unique electronic and mechanical properties with experimentally available superconductivity. .

This story is part of the Science X Dialog, where researchers can report findings from published research papers. To learn more about Science X Dialog and how to participate, visit this page.

Further information: Giovanni Alberto Ummarino et al, Can the noble metals (Au, Ag, and Cu) be superconductors?, Physical Review Materials (2024). DOI: 10.1103/PhysRevmaterials.8.L101801. For arXiv: DOI: 10.48550/arxiv.2406.16621

Biography: Alessio Zaccone received his Ph.D. He received his PhD from the Department of Chemistry, ETH Zurich in 2010. From 2010 to 2014, he was an Oppenheimer Fellow at the Cavendish Laboratory, University of Cambridge.

Since 2022, he has been Full Professor and Professor of Theoretical Physics at the Department of Physics at the University of Milan, after having served on the faculty at the Technical University of Munich (2014-2015) and the University of Cambridge (2015-2018). Awards include: ETH Silver Medal, 2020 Gauss Professorship at the Göttingen Academy of Sciences, Queen’s College Cambridge Fellowship, and ERC Consolidator Grant (‘Multimeca’).

Research contributions include exact solutions for jamming transition problems (Zaccone & Scossa-Romano PRB 2011), analytical solutions for random close-packing problems in two and three dimensions (Zaccone PRL 2022), and thermally activated reaction kinetics. Includes process theory. Shear flow (Zaccone et al. PRE 2009), theory of crystal nucleation under shear flow (Mura & Zaccone PRE 2016), theoretical prediction of boson-like peaks in vibrational spectra of crystals (Milkus & Zaccone PRB 2016; Baggioli & Zaccone PRL 2019), glass transition theory in polymers (Zaccone & Terentjev PRL 2013), discovery of well-defined topological defects in glasses (Baggioli, Kriuchevskyi, Sirk, Zaccon PRL 2021), theoretical predictions of nonmonotonicity due to phonon decay Superconducting enhancement effect (Setty, Baggioli, Zaccon PRB 2020).

Research interests range from statistical physics of disordered systems (random packing, jamming, glasses and glass transitions, colloids, non-equilibrium thermodynamics) to solid state physics and superconductivity. In 2023, he contributed the monograph “Disordered Solid Theory” (Springer, Cham, 2023).

Magazine information: arXiv

Quote: Can precious metals become superconductors? (November 7, 2024) Retrieved November 7, 2024 from https://phys.org/news/2024-11-noble-metals-superconductors.html

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