Persistence of the gapless spin liquid in the breathing kagome Heisenberg antiferromagnet

Yasir Iqbal, Didier Poilblanc, Ronny Thomale, and Federico Becca
Phys. Rev. B 97, 115127 – Published 13 March 2018
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Abstract

The nature of the ground state of the spin S=1/2 Heisenberg antiferromagnet on the kagome lattice with breathing anisotropy (i.e., with different superexchange couplings J and J within elementary up- and down-pointing triangles) is investigated within the framework of Gutzwiller projected fermionic wave functions and Monte Carlo methods. We analyze the stability of the U(1) Dirac spin liquid with respect to the presence of fermionic pairing that leads to a gapped Z2 spin liquid. For several values of the ratio J/J, the size scaling of the energy gain due to the pairing fields and the variational parameters are reported. Our results show that the energy gain of the gapped spin liquid with respect to the gapless state either vanishes for large enough system size or scales to zero in the thermodynamic limit. Similarly, the optimized pairing amplitudes (responsible for opening the spin gap) are shown to vanish in the thermodynamic limit. Our outcome is corroborated by the application of one and two Lanczos steps to the gapless and gapped wave functions, for which no energy gain of the gapped state is detected when improving the quality of the variational states. Finally, we discuss the competition with the “simplex” Z2 resonating-valence-bond spin liquid, valence-bond crystal, and nematic states in the strongly anisotropic regime, i.e., JJ.

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  • Received 13 December 2017
  • Revised 21 February 2018

DOI:https://doi.org/10.1103/PhysRevB.97.115127

©2018 American Physical Society

Physics Subject Headings (PhySH)

Condensed Matter, Materials & Applied Physics

Authors & Affiliations

Yasir Iqbal1,*, Didier Poilblanc2, Ronny Thomale3, and Federico Becca4

  • 1Department of Physics, Indian Institute of Technology Madras, Chennai 600036, India
  • 2Laboratoire de Physique Théorique UMR-5152, CNRS and Université de Toulouse, F-31062, Toulouse, France
  • 3Institute for Theoretical Physics and Astrophysics, Julius-Maximilian's University of Würzburg, Am Hubland, D-97074 Würzburg, Germany
  • 4Democritos National Simulation Center, Istituto Officina dei Materiali del CNR and SISSA-International School for Advanced Studies, Via Bonomea 265, I-34136 Trieste, Italy

  • *yiqbal@physics.iitm.ac.in

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Issue

Vol. 97, Iss. 11 — 15 March 2018

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