Exact dimer ground state of the two dimensional Heisenberg spin system SrCu_2(BO_3)_2

TL;DR

This paper discusses the exact dimer ground state of the two-dimensional Heisenberg model in SrCu_2(BO_3)_2, analyzing its quantum phase transition and experimental magnetic properties.

Contribution

It confirms the dimer ground state in SrCu_2(BO_3)_2 and determines the critical point of the quantum phase transition from dimer to Néel order.

Findings

SrCu_2(BO_3)_2 has the exact dimer ground state.

The critical value of the quantum phase transition is identified.

Triplet excitations are nearly localized, explaining magnetization plateaus.

Abstract

The two dimensional Heisenberg model for SrCu_2(BO_3)_2 has the exact dimer ground state which was proven by Shastry and Sutherland almost twenty years ago. The critical value of the quantum phase transition from the dimer state to the N\'{e}el ordered state is determined. Analysis of the experimental data shows that SrCu_2(BO_3)_2 has the dimer ground state but is close to the transition point, which leads to the unusual temperature dependence of the susceptibility. Almost localized nature of the triplet excitations explains the plateaus observed in the magnetization curve.