Since the seminal ideas of Berezinskii, Kosterlitz and Thouless, topological excitations have been at the heart of our understanding of a whole novel class of phase transitions. In most cases, those transitions are controlled by a single type of topological objects. There are, however, some situations, still poorly understood, where two dual topological excitations fight to control the phase diagram and the transition. Finding experimental realizations of such cases is thus of considerable interest. We show here that this situation occurs in BaCo2V2O8, a spin-1/2 Ising-like quasi-one-dimensional antiferromagnet, when subjected to a uniform magnetic field transverse to the Ising axis. Using neutron scattering experiments, we measure a drastic modification of the quantum excitations beyond a critical value of the magnetic field. This quantum phase transition is identified, through a comparison with theoretical calculations, to be a transition between two different types of solitonic topological object, which are captured by different components of the dynamical structure factor.

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  • 12 July 2018

    In the version of this Letter originally published, the year for ref. 30 was incorrectly listed as 2009; it should have been 2004. This has now been corrected.


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We thank R. Ballou, C. Berthier, M. Horvatić, M. Klanjšek and S. Niesen for fruitful discussions, P. Courtois and R. Silvestre for their help in the sample co-alignment carried out at ILL before the experiment at PSI, E. Villard, B. Vettard and M. Bartkowiak for their technical support during the INS experiments on ThALES (ILL), IN12 (ILL) and TASP (PSI), respectively, and J. Debray, A. Hadj-Azzem and J. Balay for their contribution to the crystal growth, cut and orientation. We acknowledge ILL and PSI for allocating neutron beam time. This work was partly supported by the French ANR Project DYMAGE (ANR-13-BS04-0013). S.T. is supported by the Swiss National Science Foundation under Division II and ImPACT project (no. 2015-PM12-05-01) from the Japan Science and Technology Agency. M.M. acknowledges funding from the Swedish Research Council (VR) through a neutron project grant (Dnr 2016-06955). T.L. acknowledges support by the Deutsche Forschungsgemeinschaft through CRC 1238 Project A02. S.C.F. is supported by JSPS KAKENHI grant no. 16J04731.

Author information


  1. Univ. Grenoble Alpes, CEA, INAC-MEM, Grenoble, France

    • Quentin Faure
    • , Stéphane Raymond
    • , Louis-Pierre Regnault
    •  & Béatrice Grenier
  2. Univ. Grenoble Alpes, Inst NEEL, Grenoble, France

    • Quentin Faure
    • , Virginie Simonet
    • , Pascal Lejay
    •  & Benjamin Canals
  3. Department of Quantum Matter Physics, University of Geneva, Geneva, Switzerland

    • Shintaro Takayoshi
    • , Christian Rüegg
    •  & Thierry Giamarchi
  4. Laboratoire Léon Brillouin, CEA, CNRS, Université Paris-Saclay, CE-Saclay, Gif-sur-Yvette, France

    • Sylvain Petit
  5. Institut Laue-Langevin, Grenoble, France

    • Martin Boehm
  6. Laboratory for Neutron Scattering and Imaging, Paul Scherrer Institut, Villigen PSI, Switzerland

    • Jonathan S. White
    • , Martin Månsson
    •  & Christian Rüegg
  7. Materials Physics, KTH Royal Institute of Technology, Stockholm, Sweden

    • Martin Månsson
  8. II. Physikalisches Institut, Universität zu Köln, Köln, Germany

    • Thomas Lorenz
  9. Condensed Matter Theory Laboratory, RIKEN, Wako, Saitama, Japan

    • Shunsuke C. Furuya


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All authors contributed significantly to this work. In detail, sample preparation was performed by P.L., neutron scattering experiments and analysis were carried out by Q.F., B.G., S.P. and V.S. with the support of S.R., L.-P.R., M.B., J.S.W., M.M. and C.R., calculations were performed by S.T., S.C.F. and T.G., inputs for the discussion of the physical results were provided by C.R., B.C. and T.L.; the manuscript was written by V.S., S.P., B.G., Q.F., T.G. and S.T. with constant feedback from the other co-authors.

Competing interests

The authors declare no competing interests.

Corresponding authors

Correspondence to Virginie Simonet or Thierry Giamarchi.

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