Z2 vortex crystal candidate in the triangular S = 1/2 quantum antiferromagnet

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Contributors

  • Jakob Nagl - , ETH Zurich (Author)
  • Kirill Yu Povarov - , Helmholtz-Zentrum Dresden-Rossendorf (HZDR) (Author)
  • Benjamin Duncan - , ETH Zurich (Author)
  • Catharina Näppi - , ETH Zurich (Author)
  • Dmitry Khalyavin - , Rutherford Appleton Laboratory (Author)
  • Pascal Manuel - , Rutherford Appleton Laboratory (Author)
  • Fabio Orlandi - , Rutherford Appleton Laboratory (Author)
  • Jeremy Sourd - , Helmholtz-Zentrum Dresden-Rossendorf (HZDR) (Author)
  • Beat Valentin Schwarze - , Helmholtz-Zentrum Dresden-Rossendorf (HZDR) (Author)
  • Freya Husstedt - , Clusters of Excellence ctd.qmat: Complexity, Topology and Dynamics in Quantum Matter, Chair of Physics of High Magnetic Fields, Helmholtz-Zentrum Dresden-Rossendorf (HZDR) (Author)
  • Sergei A. Zvyagin - , Helmholtz-Zentrum Dresden-Rossendorf (HZDR) (Author)
  • Oksana Zaharko - , Paul Scherrer Institute (PSI) (Author)
  • Paul Steffens - , ILL - Institut Laue-Langevin (Author)
  • Arno Hiess - , ILL - Institut Laue-Langevin, European Spallation Source ERIC (Author)
  • David R. Allan - , Diamond Light Source (Author)
  • Sarah A. Barnett - , Diamond Light Source (Author)
  • Zewu Yan - , ETH Zurich (Author)
  • Severian Gvasaliya - , ETH Zurich (Author)
  • Andrey Zheludev - , ETH Zurich (Author)

Abstract

The prospect of merging the paradigms of geometric frustration on a triangular lattice and bond anisotropies in the strong spin-orbit coupling limit holds tremendous promise in the search for exotic quantum materials. Here we identify a new candidate system to realize such physics, the organic quantum antiferromagnet (CD3ND3)2NaRuCl6. We report a combination of thermodynamic, magneto-elastic and neutron scattering experiments on single-crystals to determine the phase diagram in axial magnetic fields H∥c and propose a minimal model Hamiltonian. (CD3ND3)2NaRuCl6 displays an ideal triangular arrangement of Ru3+ ions adopting the spin-orbital entangled jeff = 1/2 state. It hosts residual magnetic order below TN = 0.23 K and a highly unusual H − T phase diagram including three different incommensurate states. Spin-waves in the high-field polarized regime are described by a Heisenberg triangular lattice Hamiltonian with a potential sub-leading bond dependent anisotropy term J±±. We argue that the multi-q ground state in zero magnetic field is a prime candidate for hosting the Z2 vortex crystal proposed on the triangular Heisenberg-Kitaev model. (CD3ND3)2NaRuCl6 is the first member in an extended family of quantum triangular lattice magnets, providing a new playground to study the interplay of geometric frustration and spin-orbit effects.

Details

Original languageEnglish
Article number69
Journalnpj quantum materials
Volume11
Issue number1
Publication statusPublished - Dec 2026
Peer-reviewedYes