Enhancement of magnetization plateaus in low-dimensional spin systems

Abstract

We study the low-energy properties and, in particular, the magnetization process of a spin-1/2 Heisenberg J₁−J₂ sawtooth and frustrated chain (also known as a zigzag ladder) with a spatially modulated g factor. We treat the problem both analytically and numerically while keeping the J₂/J₁ ratio generic. Numerically, we use complete and Lanczos diagonalization as well as the infinite time-evolving block decimation method. Analytically, we employ (non-)Abelian bosonization. Additionally, for the sawtooth chain, we provide an analytical description in terms of flat bands and localized magnons. By considering a specific pattern for the g-factor modulation for both models, we show that a small inhomogeneity significantly enhances a magnetization plateau at half saturation. For the magnetization of the frustrated chain, we show the destruction of one-third of the full saturation plateau in favor of the creation of a plateau at half saturation. For large values of the inhomogeneity parameter, the existence of an additional plateau at zero magnetization is possible. Here and at higher magnetic fields, the system is locked in the half-saturation plateau, never reaching full saturation.