Minimal model for the frustrated spin ladder system BiCu$_2$PO$_6$

TL;DR

This paper develops a minimal microscopic model for the frustrated spin ladder compound BiCu$_2$PO$_6$, incorporating anisotropic interactions and interladder couplings to accurately describe its excitation spectrum.

Contribution

It introduces a minimal, symmetry-based model for BiCu$_2$PO$_6$ that includes anisotropic interactions, extending the isotropic frustrated spin ladder solution with mean-field couplings.

Findings

Successfully describes low-energy dispersion of BiCu$_2$PO$_6$

Identifies key interactions responsible for non-degenerate dispersion

Provides a minimal set of parameters fitting experimental data

Abstract

To establish the microscopic model of the compound BiCu$_2$PO$_6$ is a challenging task. Inelastic neutron scattering experiments showed that the dispersion of this material is non-degenerate suggesting the existence of anisotropic interactions. Here we present a quantitative description of the excitation spectrum for BiCu$_2$PO$_6$ on the one-particle level. The solution of the isotropic frustrated spin ladder by continuous unitary transformations is the starting point of our approach. Further couplings such as isotropic interladder couplings and anisotropic interactions are included on the mean-field level. Our aim is to establish a minimal model built on the symmetry allowed interactions and to find a set of parameters, which allow us to describe the low-energy part of the dispersion without assuming unrealistic couplings.