Spin-1/2 antiferromagnetic chiral chains: the sine-Gordon model and beyond.

 · Invited

Abstract

The dramatic effect of an alternating local spin environment on the properties of the spin-1/2 antiferromagnetic chain was first discovered through high-field neutron scattering and heat capacity experiments on copper-benzoate, which revealed the development of an energy gap on application of magnetic field. This was perplexing until it was found that the behaviour of this system, and a handful of others, could be described by the sine-Gordon model of quantum-field theory. Under the influence of the applied field, the gap emerges thanks to the presence of internal staggered fields and DM interactions that are a direct result of the staggered Cu(II) octahedra.

Here, we report on the molecule-based chiral spin chain [Cu(pym)(H2O)4]SiF6.H2O (pym = pyrimidine), which at first glance could be a sine-Gordon chain, but with an added twist: a 41 screw. Electron-spin resonance, magnetometry and heat capacity measurements reveal the presence of staggered g tensors, a rich low-temperature excitation spectrum, a staggered susceptibility and a spin gap that opens on the application of a magnetic field. These phenomena are reminiscent of those previously observed in non-chiral sine-Gordon materials. In the present case, however, the size of the gap and its measured linear field dependence do not fit with the sine-Gordon model as it stands. We propose that the differences arise due to additional terms in the Hamiltonian resulting from the chiral structure.

*This project has received funding from the European Research Council (grant no. 681260). We also thank the NHMFL, EPSRC, STFC, Royal Society, NSF (grant no. DMR-1703003, DMR-1157490), DoE and the State of Florida.

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Presenters

  • Paul Goddard

    • Physics, University of Warwick
    • Department of Physics, University of Warwick, Coventry CV4 7AL, United Kingdom
    • Warwick University
    • Department of Physics, University of Warwick

Authors

  • Paul Goddard

    • Physics, University of Warwick
    • Department of Physics, University of Warwick, Coventry CV4 7AL, United Kingdom
    • Warwick University
    • Department of Physics, University of Warwick

  • Junjie Liu

    • Department of Physics, University of Oxford

  • Shunichiro Kittaka

    • Institute for Solid State Physics, University of Tokyo

  • Roger Johnson

    • University of Oxford
    • ISIS Pulsed Neutron Source, Rutherford Appleton Laboratory
    • Clarendon Laboratory, University of Oxford
    • Department of Physics, University of Oxford
    • Physics, University of Oxford

  • Tom Lancaster

    • Department of Physics, Durham University
    • Centre for Materials Physics, Durham University
    • Physics, Durham University

  • John Singleton

    • National High Magnetic Field Laboratory, Los Alamos National Laboratory
    • MPA-MAG, Los Alamos National Laboratory
    • National High Magnetic Field Laboratory, Los Alamos National Laboratory, Los Alamos, NM 87545
    • Los Alamos National Laboratory
    • NHMFL, Los Alamos National Labs
    • NHMFL, Los Alamos National Laboratory
    • Los Alamos, National High Magnetic Field Laboratory
    • NHMFL, Los Alamos Natl Lab
    • Los Alamos Natl Lab

  • Toshiro Sakakibara

    • Institute for Solid State Physics, University of Tokyo
    • ISSP, University of Tokyo

  • Yoshimitsu Kohama

    • ISSP, Tokyo University
    • The Institute for Solid State Physics, University of Tokyo
    • Institute for Solid State Physics, University of Tokyo
    • The Institute for Solid State Physics, The University of Tokyo

  • Johan Van Tol

    • National High Magnetic Field Laboratory
    • National High Magnetic Field Laboratory, Florida State University
    • National High Magnetic Field Lab

  • Arzhang Ardavan

    • Department of Physics, University of Oxford
    • University of Oxford

  • Ben Heathcote Williams

    • Department of Physics, University of Oxford

  • Stephen Blundell

    • University of Oxford
    • Oxford University
    • Department of Physics, University of Oxford

  • Zachary Manson

    • Chemistry, Eastern Washington University
    • Department of Chemistry and Biochemistry, Eastern Washington University

  • Jamie Manson

    • Chemistry, Eastern Washington University
    • Dept. of Chemistry and Biochemistry, Eastern Washington University
    • Eastern Washington University
    • Department of Chemistry and Biochemistry, Eastern Washington University