Intervening alternative spin-liquid saddle

Determine whether a different projective-symmetry-allowed spin-liquid saddle intervenes before the magnetic instability is reached in the spin-$S$ Kitaev-Heisenberg model.

Background

The calculation uses the c0/2c0/2-flux Schwinger-boson mean-field saddle of the pure Kitaev model as a fixed reference state and identifies the magnetic phase boundary from the divergence of the RPA susceptibility. The saddle point is not allowed to evolve self-consistently under the perturbing Heisenberg interaction.

Because multiple projective-symmetry-allowed Schwinger-boson Ansätze may compete, the fixed-saddle analysis does not establish that the selected spin-liquid state remains the relevant state all the way to the magnetic instability. A systematic comparison of competing Ansätze is therefore required to determine whether another spin-liquid phase intervenes first.

References

Whether a different spin-liquid saddle intervenes before the magnetic instability is reached would also need to be examined by comparing multiple projective-symmetry-allowed Ansätze.

— Schwinger boson perturbation theory for spin-$S$ Kitaev-Heisenberg magnets: phase diagram and dynamical response near Kitaev spin liquids  (2609.08548 - Sasamoto et al., 8 Sep 2026) in Section 5.2, “Dynamical signatures of the magnetic instability”