Quantum-classical crossover in the spin-1/2 Heisenberg-Kitaev kagome magnet

In our recent work [1], we revisit the crossover from the quantum resonating valence bond (RVB) phase to a semiclassical regime brought about by anisotropic Kitaev interactions in the spin-1/2 Heisenberg kagome antiferromagnet, and focus on the precise mechanisms underpinning this crossover. We parametrize the classical ground states (GSs) in terms of emergent Ising-like variables, and use this: i) to construct an effective low-energy description of the order-by-disorder mechanism, and ii) to contrast, exact diagonalization data obtained from the full basis with that obtained from the restricted basis of classical GSs. The results reveal that fluctuation corrections from states outside the restricted basis are strongly quenched in the semiclassical regime, and the RVB phase survives up to a relatively large value of Kitaev anisotropy K. Moreover the pure Kitaev model admits a subextensive number of one-dimensional symmetries, which explains the absence of classical and quantum order by disorder.

[1] Yang Yang, Natalia B. Perkins, Fulya Koç, Chi-Huei Lin, Ioannis Rousochatzakis, Phys. Rev. Research 2, 033217 (2020)