Spontaneous dimer order, excitation spectrum, and quantum phase transitions in the J1-J2 Heisenberg model

TL;DR

This paper investigates the ground state, excitation spectrum, and phase transitions of the two-dimensional frustrated J1-J2 Heisenberg antiferromagnet, highlighting the role of spontaneous dimer order and low-energy singlet states.

Contribution

It provides new insights into the stability and structure of the excitation spectrum, especially near the quantum critical point, and discusses the nature of dimer order in the disordered phase.

Findings

Spontaneous dimer order exists in the quantum disordered phase.

The two-particle singlet excitation branch persists throughout the disordered phase.

Near the critical point, the dimer order parameter indicates the presence of low-energy singlet bound states.

Abstract

We overview some recent work and present new results on the ground state properties and the spectrum of excitations of the two-dimensional frustrated Heisenberg antiferromagnet. Spontaneous dimer order is present in the quantum disordered phase of this model. We study the stability and analyze the structure of the spectrum, including the two-particle singlet excitation branch throughout the disordered phase, as well as in the vicinity of the Neel critical point. The variation of the dimer order parameter is also given, and it is argued that near the critical point it reflects the presence of the low-energy singlet bound state.