Vanishing spin gap in a competing spin-liquid phase in the kagome Heisenberg antiferromagnet

  title={Vanishing spin gap in a competing spin-liquid phase in the kagome Heisenberg antiferromagnet},
  author={Yasir Iqbal and Didier Poilblanc and Federico Becca},
  journal={Physical Review B},
We provide strong numerical evidence, using improved variational wave functions, for a ground state with vanishing spin gap in the spin-$1/2$ quantum Heisenberg model on the kagome lattice. Starting from the algebraic $U(1)$ Dirac spin liquid state proposed by Ran et al. [Phys. Rev. Lett. 98, 117205 (2007)] and iteratively applying a few Lanczos steps, we compute the lowest $S=2$ excitation constructed by exciting spinons close to the Dirac nodes. Our results are compatible with a vanishing… 

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