Contractor-Renormalization approach to frustrated magnets in magnetic field

TL;DR

This paper introduces the use of the Contractor Renormalization (CORE) technique to derive effective models for frustrated quantum magnets in magnetic fields, successfully capturing phenomena like magnetization plateaux beyond perturbation theory.

Contribution

It demonstrates how CORE can effectively analyze frustrated spin ladders and bilayers, providing insights into magnetization phenomena with a non-perturbative approach.

Findings

CORE reproduces magnetization plateaux in phase diagrams

Effective models match known behaviors of frustrated magnets

Addresses plateau formation in 2D bilayers

Abstract

We propose to use the Contractor Renormalization (CORE) technique in order to derive effective models for quantum magnets in a magnetic field. CORE is a powerful non-perturbative technique that can reduce the complexity of a given microscopic model by focusing on the low-energy part. We provide a detailed analysis of frustrated spin ladders which have been widely studied in the past: in particular, we discuss how to choose the building block and emphasize the use of their reduced density matrix. With a good choice of basis, CORE is able to reproduce the existence or not of magnetization plateaux in the whole phase diagram contrary to usual perturbation theory. We also address the issue of plateau formation in two-dimensional bilayers and point out the analogy between non-frustrated strongly anisotropic models and frustrated SU(2) ones.