Indications of a Metallic Antiferromagnetic Phase in the 2 Dimensional $U-t-t'$ Model

TL;DR

This paper provides evidence from mean-field and quantum Monte Carlo methods for a metallic antiferromagnetic phase in a two-dimensional $U-t-t'$ model, highlighting a transition from antiferromagnetic order to an insulating state.

Contribution

It introduces the possibility of a metallic antiferromagnetic phase in the 2D $U-t-t'$ model, supported by computational results, which is a novel insight into the phase diagram of this system.

Findings

Antiferromagnetic order develops at $U_{c_1}/t \\approx 2.5$.

The system becomes insulating at larger couplings, $4 < U_{c_2}/t < 6$.

Evidence suggests a metallic antiferromagnetic phase exists between these transitions.

Abstract

We present mean-field and quantum Monte Carlo results that suggest the existence of an itinerant antiferromagnetic ground state in the half-filled $U-t-t'$ model in two dimensions. In particular, working at $t'/t=-0.2$ we found that antiferromagnetic long range order develops at $U_{c_1}/t\approx 2.5$, while a study of the density of states $N(\omega)$ and the response to an external magnetic field indicates that the system becomes insulating at a larger coupling $4<U_{c_2}/t<6$.