Non-fermi liquid behavior in itinerant antiferromagnets

TL;DR

This paper demonstrates that in a two-dimensional itinerant antiferromagnet near a quantum critical point, fermionic excitations exhibit non-Fermi liquid behavior with a self-energy scaling as ω^{2/3}, due to coupling with spin fluctuations.

Contribution

It reveals a non-Fermi liquid state in itinerant antiferromagnets near quantum criticality, challenging the conventional Fermi liquid paradigm.

Findings

Fermionic self-energy scales as ω^{2/3} at low frequencies.

Longitudinal spin susceptibility dissolves into Landau damping.

Transverse spin fluctuations exhibit overdamped behavior near criticality.

Abstract

We consider a two dimensional itinerant antiferromagnet near a quantum critical point. We show that, contrary to conventional wisdom, fermionic excitations in the ordered state are not the usual Fermi liquid quasiparticles. Instead, down to very low frequencies, the fermionic self energy varies as $\omega^{2/3}$. This non-Fermi liquid behavior originates in the coupling of fermions to the longitudinal spin susceptibility $\chi_{\parallel}(q, \Omega)$ in which the order-induced ``gap'' in the spectrum at $q=0$ dissolves into the Landau damping term at $v_F q >\Omega$. The transverse spin fluctuations obey $z=1$ scaling characteristic of spin waves, but remain overdamped in a finite range near the critical point.