Green's function approach to quantum criticality in the anisotropic Kondo-necklace model

TL;DR

This paper investigates the quantum phase transition in the two-dimensional anisotropic Kondo-necklace model using Green's function and bond operator formalism, revealing how anisotropies influence critical behavior.

Contribution

It introduces a Green's function approach with hard core repulsion to analyze quantum criticality, extending previous bond operator mean field studies for the anisotropic Kondo-necklace model.

Findings

Identified the gapless excitations at the quantum critical point.

Analyzed the effects of inter-site and local anisotropies on the critical point.

Compared results with previous mean field calculations.

Abstract

We have studied the quantum phase transition between the antiferromagnetic and spin liquid phase for the two dimensional anisotropic Kondo-necklace model. The bond operator formalism has been implemented to transform the spin Hamiltonian to a bosonic one. We have used the Green's function approach including a hard core repulsion to find the low energy excitation spectrum of the model. The bosonic excitations become gapless at the quantum critical point where the phase transition from the Kondo singlet state to long range antiferromagnetic order takes place. We have studied the effect of both inter-site (delta) and local (Delta) anisotropies on the critical point and on the critical exponent of the excitation gap in the paramagnetic phase. We have also compared our results with previous bond operator mean field calculations.