Theory of the Kitaev model in a [111] magnetic field

Previous numerical work has predicted a new spin liquid phase in the antiferromagnetic Kitaev model at intermediate magnetic fields; however, its nature is not easily discernible by numerical approaches. Here, by using a variational approach, the authors show that this phase is a gapped Abelian spin liquid Recent numerical studies indicate that the antiferromagnetic Kitaev honeycomb lattice model undergoes a magnetic-field-induced quantum phase transition into a new spin-liquid phase. This intermediate-field phase has been previously characterized as a gapless spin liquid. By implementing a recently developed variational approach based on the exact fractionalized excitations of the zero-field model, we demonstrate that the field-induced spin liquid is gapped and belongs to Kitaev's 16-fold way. Specifically, the low-field non-Abelian liquid with Chern number C = +/- 1 transitions into an Abelian liquid with C = +/- 4. The critical field and the field-dependent behaviors of key physical quantities are in good quantitative agreement with published numerical results. Furthermore, we derive an effective field theory for the field-induced critical point which readily explains the ostensibly gapless nature of the intermediate-field spin liquid.

Automated summary

This study reveals the existence of a gapped spin liquid phase in the antiferromagnetic Kitaev model at intermediate magnetic fields through the use of a variational approach. Furthermore, the characteristics and critical behaviors of this phase are investigated, providing valuable insights into the nature of the spin liquid.