Raman study of KNi$_2$Se$_2$ and KNi$_2$S$_2$: an origin of re-entrant transition in KNi$_2$Se$_2$

ORAL

Abstract

The unusual phenomena of an increase in symmetry upon cooling due to a re-entrant transition can be associated with electronic correlations. In KNi$_2$Se$_2$ our vibrational Raman spectroscopy study identifies regular Ni-atoms displacements, which disappear below approximately 50 K resulting in an increase of symmetry of the unit cell. At low temperatures heavy fermion behavior with m$_{eff}$ of about 20m$_e$ is observed [1]. To find the origin of this untypical high-temperature behavior, we compare our results on KNi$_2$Se$_2$ with that of the sister-compound KNi$_2$S$_2$ [2], where Raman spectroscopy does not observe clear evidence of the high-temperature symmetry breaking, but the heavy fermion effect is still present. \\[4pt] [1] J. R. Neilson et al. Phys. Rev. B (2012), 86, 054512.\\[0pt] [2] J. R. Neilson et al. Phys. Rev. B (2013), 87, 045124

*The work is supported by DOE grant for The Institute of Quantum Matter DE-FG02-08ER46544.

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Authors

  • Natalia Drichko

    • Department of Physics and Astronomy, The Johns Hopkins University

  • James Neilson

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

  • Tyrel McQueen

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