Kitaev materials beyond iridates: Order by quantum disorder and Weyl magnons in rare-earth double perovskites

Fei-Ye Li, Yao-Dong Li, Yue Yu, Arun Paramekanti, and Gang Chen
Phys. Rev. B 95, 085132 – Published 22 February 2017

Abstract

Motivated by the experiments on the rare-earth double perovskites, we propose a generalized Kitaev-Heisenberg model to describe the generic interaction between the spin-orbit-entangled Kramers doublets of the rare-earth moments. We carry out a systematic analysis of the mean-field phase diagram of this new model. In the phase diagram, there exist large regions with a continuous U(1) or O(3) degeneracy. Since no symmetry of the model protects such a continuous degeneracy, we predict that the quantum fluctuation lifts the continuous degeneracy and favors various magnetic orders in the phase diagram. From this order by quantum disorder mechanism, we further predict that the magnetic excitations of the resulting ordered phases are characterized by nearly gapless pseudo-Goldstone modes. We find that there exist Weyl magnon excitations for certain magnetic orders. We expect our prediction to inspire further study of Kitaev physics, the order by quantum disorder phenomenon, and topological spin-wave modes in the rare-earth magnets and the systems alike.

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  • Received 26 July 2016
  • Revised 26 October 2016

DOI:https://doi.org/10.1103/PhysRevB.95.085132

©2017 American Physical Society

Physics Subject Headings (PhySH)

Condensed Matter, Materials & Applied Physics

Authors & Affiliations

Fei-Ye Li1, Yao-Dong Li2, Yue Yu2,4, Arun Paramekanti3, and Gang Chen2,4,5,*

  • 1CAS Key Laboratory of Theoretical Physics, Institute of Theoretical Physics, Chinese Academy of Sciences, Beijing 100190, People's Republic of China
  • 2State Key Laboratory of Surface Physics, Center for Field Theory and Particle Physics, Department of Physics, Fudan University, Shanghai 200433, People's Republic of China
  • 3Department of Physics, University of Toronto, Toronto, Ontario, Canada M5S 1A7 and Canadian Institute for Advanced Research, Toronto, Ontario, Canada M5G 1Z8
  • 4Collaborative Innovation Center of Advanced Microstructures, Nanjing 210093, People's Republic of China
  • 5Perimeter Institute for Theoretical Physics, Waterloo, Ontario, Canada N2L 2Y5

  • *gangchen.physics@gmail.com, gchen_physics@fudan.edu.cn

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Vol. 95, Iss. 8 — 15 February 2017

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