Rapid filling of the spin gap with temperature in the Schwinger-boson mean-field theory of the antiferromagnetic Heisenberg kagome model

Abstract

Using Schwinger-boson mean-field theory, we calculate the dynamic spin structure factor at low temperatures $0<T\ll J$ for the spin-$1/2$ antiferromagnetic Heisenberg kagome model, within the gapped ${\mathbb{Z}}_2$ spin liquid phase Ansatz. We find that the spectral gap rapidly fills with temperature, with robust low-energy spectral weight developing by a temperature of $\Delta /3$, where the spin gap is $2\Delta$ (i.e., $\Delta$ is the spinon gap), before any appreciable rise in spinon density or change in zero-temperature mean-field parameters. This is due to deconfinement of spinons which leads to terms suppressed only by $\exp (-\Delta /T)$. At still higher temperatures, the spinon density increases rapidly leading to a breakdown of the Schwinger-boson mean-field approach. We suggest that if the impurity-free spectral functions can be obtained through neutron scattering experiments on kagome herbertsmithites, temperature dependence of the subgap weight can provide distinct signatures of a ${\mathbb{Z}}_2$ quantum spin liquid.

Accepted version, journal article, 17 pages, 12 figures, including 4 appendices

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Cited by in corpus (7)

• Finite-temperature properties of the Kitaev-Heisenberg models on kagome and triangular lattices studied by improved finite-temperature Lanczos methods
• Thermodynamics of the pyrochlore-lattice quantum Heisenberg antiferromagnet
• How correlations change the magnetic structure factor of the kagome Hubbard model
• Dynamics of fractionalized mean-field theories: consequences for Kitaev materials
• Schwinger boson theory for $S=1$ Kitaev quantum spin liquids
• Dynamical spin correlations in kagome antiferromagnets: comparison of Abrikosov fermion and Schwinger boson approaches beyond mean field
• Vison condensation and spinon confinement in a kagome-lattice ${\mathbb{Z}}_2$ spin liquid: A numerical study of a quantum dimer model