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 zig-zag ladder) with a spatially anisotropic 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 (iTEBD) 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 anisotropy for both models, we show that a small anisotropy significantly enhances a magnetization plateau at half saturation. For the magnetization of the frustrated chain, we show the destruction of the 1/3 of the full saturation plateau in favor of the creation of a plateau at half-saturation. For large anisotropies, 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.