Robust semiclassical magnetization plateau in the kagome lattice

TL;DR

This paper demonstrates that a semiclassical approach effectively captures the robust 1/3 magnetization plateau in the kagome lattice, providing insights into its stabilization mechanism and quantitative predictions consistent with experiments.

Contribution

It introduces a semiclassical analysis of the kagome Heisenberg model, revealing the plateau's robustness and the role of quantum fluctuations, with accurate predictions from linear spin-wave theory.

Findings

Robust 1/3 magnetization plateau exists for both signs of J2.

Plateau width shows weak dependence on J2.

A magnetization jump at saturation occurs only at J2=0.

Abstract

Inspired by recent observations of the $1/3$ magnetization plateau in kagome-based magnets, we investigate the $J_1-J_2$ Heisenberg model on the kagome lattice under the influence of an external magnetic field. Although the classical ground state at zero field depends on the sign of $J_2$, we find a robust $1/3$ semiclassical magnetization plateau in both cases. The mechanism that stabilizes this plateau is analogous to that observed in the triangular lattice, where quantum fluctuations select a collinear state from the degenerate classical manifold. We calculate the plateau width, which shows a weak dependence on $J_2$, using nonlinear spin-wave theory. Additionally, we find that a straightforward approach based on linear spin-wave yields quantitatively accurate results even for $S=1/2$. Furthermore, we identify a magnetization jump at the saturation field when $J_2=0$; this jump is related to the presence of a flat band and disappears for $J_2 \neq 0$. Our study demonstrates that a semiclassical approach effectively captures the $1/3$ plateau in the kagome lattice and serves as a valuable tool for interpreting experimental and numerical results alike.