Quantum freezing and re-entrant melting in a quantum spin liquid

ORAL

Abstract

Exchange interactions in piperazinium hexachlorodicuprate (PHCC) produce a frustrated bilayer antiferromagnet. We report the field-temperature phase diagram of this system as determined via high field (up to H = 50 T) susceptibility and neutron scattering (H = 14.2 T) experiments. There are two quantum critical points: Hc1=7.6 T separates the singlet phase from a three dimensional spin-ordered state while Hc2=37 T marks the onset of saturated ferromagnetism. The long range ordered phase is embedded in a gapless quasi-two dimensional paramagnetic regime with short range spin correlations. Close to the low field quantum critical point, a reentrant phase transition between long range order and the singlet phase indicates that weak interactions with lattice or nuclear spin degrees of freedom become important.

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Authors

  • Collin Broholm

    • Johns Hopkins University, Baltimore, MD 21210

  • Matthew Stone

    • Condensed Matter Sciences Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831

  • Igor Zaliznyak

    • Brookhaven National Laboratory
    • Brookhaven National Laboratory, Upton, NY 11973

  • Daniel Reich

    • Johns Hopkins University, Baltimore, MD 21210
    • Johns Hopkins University

  • Peter Vorderwisch

    • Hahn-Meitner Institut, D-14109 Berlin, Germany

  • Neil Harrison

    • National High Magnetic Field Laboratory, Los Alamos, NM 87545