Quantum Materials: Superconductor peaks under pressure
Researchers at the Karlsruhe Institute of Technology (KIT) from Helmholtz Information and at the Max Planck Institute for Chemical Physics of Solids (MPI CPfS) in Dresden have now determined that mechanical pressure increases superconductivity and simultaneously makes the material easier to deform. They attribute this to quantum mechanical excitations of the electrons. Their work contributes to understanding the interplay of elastic and electronic properties. (Source: Karlsruhe Institute of Technology – Press Releases)
Superconductors are materials that show no electrical resistance below a certain temperature, known as the critical temperature. This makes them of interest for various applications in energy conversion and distribution. For Strontium Ruthenate (Sr2RuO4), science has not yet understood how superconductivity occurs. “Conventional theory does not apply to Strontium Ruthenate. However, quantum mechanics takes us further, as it allows us not only to describe the properties of individual atoms and molecules, but also the collective properties of many-particle systems,” says Professor Jörg Schmalian, head of the Institute for Theory of Condensed Matter (TKM) at KIT and head of the Department of Theory of Quantum Materials at the Institute for Quantum Materials and Technologies (IQMT) at KIT.
Mechanical Pressure Along a Direction Increases Critical Temperature
Schmalian is one of the main authors of the study published in the journal Science. Researchers at several KIT institutes and at MPI CPfS had already demonstrated in a 2022 publication in the journal Nature how mechanical pressing along a certain direction can significantly increase the critical temperature of Strontium Ruthenate and alter the excitation behavior of the electrons. Together with international partners, the researchers from Karlsruhe and Dresden now found that this very pressure, which greatly enhances superconductivity, makes the material significantly softer mechanically, facilitating deformations. They attribute this to a quantum mechanical resonance of the vibrations of the electrons.
About 60 years ago, the Soviet physicist Ilja M. Lifshitz predicted a mechanical softening, now known as Lifshitz transition. “However, the effect we have now identified is more than a thousand times greater and can be clearly linked to the enhancement of superconductivity. This is astonishing because less than one percent of the total electrons in the material force a reduction of the elastic constants by 20 percent,” explains Schmalian.
A Few Current-Carrying Electrons Call the Shots
The study of the interplay between elastic and electronic properties is also the focus of the Transregio ELASTO-Q-MAT, funded by the German Research Foundation (DFG), in which MPI CPfS and KIT are heavily involved. For the study published in Science, KIT researchers developed a model of the effect in which a few of the current-carrying electrons dominate and can make the material much softer. The measurements for this were carried out at MPI CPfS in Dresden. “Ilja M. Lifshitz made no mistake in his theory,” emphasizes Schmalian. “However, our study offers a new perspective and opens up the possibility of manipulating strong quantum fluctuations in the laboratory in the future and optimizing materials for a given physical effect.
KIT/I. Hartmann, 07.11.2023
Note: The article has been translated from German to English. It is based on a press release from the Karlsruhe Institute of Technology (KIT).
The original press release can be found at:
Quantenmaterialien: Supraleiter läuft unter Druck zur Hochform auf (only in german)
The original publication can be found at:
H. M. L. Noad, K. Ishida, Y.-S. Li, E. Gati, V. Stangier, N. Kikugawa, D. A. Sokolov, M. Nicklas, B. Kim, I. I. Mazin, M. Garst, J. Schmalian, A. P. Mackenzie, and C. W. Hicks: Giant lattice softening at a Lifshitz transition in Sr2RuO4. Science, 2023. DOI: 10.1126/science.adf3348
Localization in the Helmholtz Research Field Information:
Helmholtz Research Field Information, Program 2: Natural, Artificial and Cognitive Information Processing, Topic 1: Quantum Materials
Contact:
Prof. Dr. Jörg Schmalian
Head of the Institute for Theory of Condensed Matter (TKM)
head of the Department of Theory of Quantum Materials at the Institute for Quantum Materials and Technologies (IQMT)
Karlsruhe Institute of Technology (KIT)
Phone: +49 721 608-43430
E-Mail: joerg.schmalian@kit.edu
Contact for this press release:
Isabelle Hartmann
Press Officer
Karlsruhe Institute of Technology (KIT)
Phone: +49 721 608-41175
E-Mail: i.hartmann@kit.edu
