Spin-Wave Excitations of Half-Filled Kondo Lattice Model

TL;DR

This paper investigates spin-wave excitations in the antiferromagnetic phase of the half-filled Kondo lattice model, calculating spectra and thermodynamic properties, and deriving an expression for the Néel temperature in three dimensions.

Contribution

It introduces a decoupling approximation for spin Green's functions to analyze spin excitations and derives a formula for the Nél temperature in the weak-coupling limit.

Findings

Néel temperature scales as 0.087J^2 ln(1/J) in 3D.

Spin-wave velocity to Néel temperature ratio increases as Kondo coupling decreases.

Long-range effective interactions are reflected in the enhanced ratio.

Abstract

The spin excitations in the antiferromagnetic phase of half-filled Kondo lattice model are studied by means of the decoupling approximation for spin Green's function. The spin-wave spectrum is calculated as a function of Kondo coupling, and this is used to calculate the thermodynamic quantities at low temperatures. The N\'{e}el temperature of the form $T_{\rm N}=0.087{J}^2\ln{(1/J)}$ is obtained for the 3-dimensional case in the weak-coupling limit. It is pointed out that the ratio of the spin-wave velocity to the N\'{e}el temperature $v_s/T_{\rm N}$ is enhanced as the Kondo coupling becomes small, reflecting the long-range nature of effective interactions between localized spins.