Spiral ferrimagnetic phases in the two-dimensional Hubbard model

TL;DR

This study explores the phase diagram of the 2D Hubbard model, revealing stable spiral ferrimagnetic phases at intermediate interaction strengths and doping levels, with phase transitions to non-spiral ferrimagnetic states at higher interactions.

Contribution

It introduces the existence of spiral ferrimagnetic phases in the mean-field phase diagram of the 2D Hubbard model, highlighting their stability at specific interaction and doping ranges.

Findings

Spiral ferrimagnetic phases are most stable for $6 \,\lesssim\, U/t \lesssim 11$.

Higher $U$ values favor non-spiral ferrimagnetic phases.

Phase separation leads to coexistence of spiral and non-spiral ferrimagnetic phases at fixed density.

Abstract

We address the possibility of spiral ferrimagnetic phases in the mean-field phase diagram of the two-dimensional (2D) Hubbard model. For intermediate values of the interaction $U$ ($6 \lesssim U/t \lesssim 11$) and doping $n$, a spiral ferrimagnetic phase is the most stable phase in the $(n,U)$ phase diagram. Higher values of $U$ lead to a non-spiral ferrimagnetic phase. If phase separation is allowed and the chemical potential $\mu$ replaces the doping $n$ as the independent variable, the $(\mu,U)$ phase diagram displays, in a considerable region, a spiral (for $6 \lesssim U/t \lesssim 11$) and non-spiral (for higher values of $U$) ferrimagnetic phase with fixed particle density, $n=0.5$, reflecting the opening of an energy gap in the mean-field quasi-particle bands.