Physical realization and identification of topological excitations in quantum Heisenberg ferromagnet on lattice

TL;DR

This paper investigates topological excitations like quantum vortices in a quantum Heisenberg ferromagnet on a lattice, emphasizing the role of the Wess-Zumino term in identifying and characterizing these excitations, especially in the strongly quantum regime.

Contribution

It introduces a novel formalism for constructing quantum vortices using the Wess-Zumino term, distinguishing odd and even topological charges and their behavior across different spin regimes.

Findings

Wess-Zumino term effectively identifies a broad class of vortices.

Odd topological charge excitations exhibit self-similar internal charge distribution.

Behavior of topological excitations varies significantly between quantum and higher spin regimes.

Abstract

Physical spin configurations corresponding to topological excitations expected to be present in the XY limit of a purely quantum spin 1/2 Heisenberg ferromagnet, are probed on a two dimensional square lattice. Quantum vortices (anti-vortices) are constructed in terms of coherent spin field components as limiting case of meronic (anti-meronic) configurations. The crucial role of the associated Wess-Zumino term is highlighted in our procedure. It is shown that this term can identify a large class of vortices (anti-vortices). In particular the excitations having odd topological charges form this class and also exihibit a self-similar pattern regarding the internal charge distribution. This manifestation of different behaviour of the odd and the even topological sectors is very prominent in the strongly quantum regime but fades away as we go to higher spins. Our formalism is distinctly different from the conventional approach for the construction of quantum vortices (anti-vortices).