Spin-phonon interactions on the kagome lattice: Dirac spin liquid versus valence-bond solids
arxiv(2023)
摘要
We investigate the impact of the spin-phonon coupling on the S=1/2 Heisenberg
model on the kagome lattice. For the pure spin model, there is increasing
evidence that the low-energy properties can be correctly described by a Dirac
spin liquid, in which spinons with a conical dispersion are coupled to emergent
gauge fields. Within this scenario, the ground-state wave function is well
approximated by a Gutzwiller-projected fermionic state [Y. Ran, M. Hermele,
P.A. Lee, and X.-G. Wen, Phys. Rev. Lett. 98, 117205 (2007)]. However, the
existence of U(1) gauge fields may naturally lead to instabilities when small
perturbations are included. Since phonons are ubiquitous in real materials,
they may play a relevant role in the determination of the actual physical
properties of the kagome antiferromagnet. We perform a step forward in this
direction, including phonon degrees of freedom (at the quantum level) and
applying a variational approach based upon Gutzwiller-projected fermionic
Ansätze. Our results suggest that the Dirac spin liquid is stable for small
spin-phonon couplings, while valence-bond solids are obtained at large
couplings. Even though different distortions can be induced by the spin-phonon
interaction, the general aspect is that the energy is lowered by maximizing the
density of perfect hexagons in the dimerization pattern.
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