Itinerant antiferromagnetism in infinite dimensional Kondo lattice

Highly accurate numerical results for single-particle spectrum and order parameter are obtained for the magnetically ordered Kondo lattice by means of the dynamical mean-field theory combined with the continuous-time quantum Monte Carlo method. Hybridized energy bands involving local spins are identified in the Néel state as a hallmark of itinerant antiferromagnetism. At the boundary of the reduced Brillouin zone, the twofold degeneracy remains in spite of the doubled unit cell. This degeneracy results if the molecular field felt by localized spins has identical magnitude and reversed direction with that of conduction electrons. The persistent Kondo effect is responsible for the behavior. The antiferromagnetic quantum transition occurs inside the itinerant regime and does not accompany the itinerant-localized transition.

Figure 1

(Color online) Staggered spin polarization $2⟨S_{\mathit{Q}}^z⟩$ (left scale) as a function of temperature for different values of $J$. Also shown is the inverse staggered susceptibility ${\chi }_{\mathit{Q}}^{-1}$ (right scale), which goes to zero at $T_{\text{N}}$.

Figure 2

(Color online) $J$ dependence of the density of states for the conduction electron and with $T\sim 0$.

Figure 3

(Color online) $J$ dependence of the energy gap ${\Delta }_{\text{c}}/2$. For comparison, also plotted are $J⟨S^z⟩$, $J⟨s_{\text{c}}^z⟩$; $S^z$ and $s_{\text{c}}^z$ are the localized and conduction spins at a local site, respectively. ${\tilde{V}}^2/D$ represents the effective hybridization to be explained later, and $T_{\text{K}}$ is the Kondo temperature defined by Eq. (3).

Figure 4

(Color online) Single-particle spectrum with $J=0.2$ in (a) paramagnetic phase at $T=0.035$ and (b) antiferromagnetic phase at $T=0.010$.

Figure 5

(Color online) $A_{\sigma }\left(\kappa ,\omega \right)$ with ferromagnetic interaction $J=-0.2$ in (a) paramagnetic phase at $T=0.035$ and (b) antiferromagnetic phase at $T=0.010$.