Local increase of symmetry on cooling in KNi$_2$Se$_2$

ORAL

Abstract

Materials with the ThCr$_2$Si$_2$-type structure host myriad examples of many-body physics, including high-temperature superconductivity and heavy fermion behavior. In these compounds, the emergence of the collective electronic state frequently occurs near a magnetic instability, suggesting that magnetic fluctuations underlie the electronic phenomena. I will provide evidence for similar many-body physics in the structurally related, but non-magnetic compound, KNi2Se2. KNi$_2$Se$_2$ exhibits an increase of symmetry on cooling below $T\le 50$ K, as observed by Raman spectroscopy and high-resolution synchrotron x-ray diffraction. X-ray absorption spectroscopy confirms that the symmetry increase is due to changes in nickel-nickel interactions and suppression of charge density wave fluctuations. Density functional theory calculations reveal a zone-boundary lattice instability that provides a model of the room-temperature x-ray pair distribution function data, but fails to describe the higher local symmetry observed for $T\le 50$ K. Together, these results support many-body correlation effects as drivers for the unusual heavy fermion electronic ground state in KNi$_2$Se$_2$.

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Authors

  • James Neilson

    • Colorado State University
    • Department of Chemistry, Colorado State University

  • Natalia Drichko

    • Johns Hopkins University

  • Anna Llobet

    • Los Alamos National Laboratory

  • Mahalingham Balasubramanian

    • Argonne National Laboratory

  • Matthew Suchomel

    • Argonne National Laboratory

  • Tyrel McQueen

    • Johns Hopkins University
    • Department of Chemistry, Department of Physics and Astronomy The Johns Hopkins University
    • The Johns Hopkins University