Varied Perturbation Theory for the Dispersion Dip in the Two-Dimensional Heisenberg Quantum Antiferromagnet

Abstract

We study the roton-like dip in the magnon dispersion at the boundary of the Brillouin zone in the isotropic S=1/2 Heisenberg quantum antiferromagnet. This high-energy feature is sometimes seen as indication of a fractionalization of the magnons to spinons. In this article, we provide evidence that the description of the dip in terms of magnons can be improved significantly by applying more advanced evaluation schemes. In particular, we illustrate the usefulness of the application of the principle of minimal sensitivity in varied perturbation theory. Thereby, we provide an example for the application of this approach to an extended condensed matter problem governed by correlations which can trigger analogous investigations for many other systems.

Published version

References in corpus (4)

• Anomalous High-Energy Spin Excitations in La2CuO4
• Quantum dynamics and entanglement of spins on a square lattice
• Enhanced Perturbative Continuous Unitary Transformations
• Effects of ring exchange interaction on the Neel phase of two-dimensional, spatially anisotropic, frustrated Heisenberg quantum antiferromagnet

Cited by in corpus (8)

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• Continuous similarity transformation for critical phenomena: easy-axis antiferromagnetic XXZ model
• Quantum melting of long-range ordered quantum antiferromagnets investigated by momentum-space continuous similarity transformations
• Spin dynamics of antiferromagnetically coupled ferromagnetic bilayers -- the case of Cr${}_2$WO${}_6$ and Cr${}_2$MoO${}_6$
• Breakdown of the conventional spin-wave dynamics and its double-constraint modification in the spin-$\frac{1}{2}$ triangular-prism Heisenberg antiferromagnet