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.

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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