The Kekulé-Kitaev model: linear and non-linear responses and magnetic field effects

Abstract

The Kekulé-Kitaev model, an extension of the Kitaev model, exhibits quantum spin liquid (QSL) properties, which has an exact solution through Kitaev parton construction. In this study, we calculate the dynamical spin structure factor as a linear response and the third-order magnetic susceptibility as a nonlinear response using two-dimensional coherent spectroscopy for Kekulé-Kitaev model. Our results reveal that the few-matter fermion excitations approximation provides reliable results for both linear and nonlinear responses. Notably, while the Kekulé-Kitaev model shows linear and nonlinear responses qualitatively similar to the Kitaev model, it displays distinct behavior under a weak uniform/staggered magnetic field. Specifically, the Kekulé-Kitaev model does not present a non-Abelian phase under a uniform magnetic field, while such phase appears in the presence of a staggered magnetic field. Interestingly, within the non-Abelian phase, signals originating from two non-adjacent fluxes in the nonlinear response are stronger than signals from other flux excitations. Furthermore, We demonstrate that the ground state of the Kekulé-Kitaev model at isotropic coupling is mapped, through unitary spin rotations, to an excited state of the Kitaev model with a uniform flux configuration.

18 pages, 13 figures, to appear in PRB

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Cited by in corpus (1)

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