Magnetic phase transitions and unusual antiferromagnetic states in the Hubbard model

TL;DR

This paper explores magnetic phase transitions in the Hubbard model on square and cubic lattices, revealing complex antiferromagnetic states and phase separation phenomena using the slave-boson approach.

Contribution

It provides new insights into the magnetic phase diagrams and identifies two distinct antiferromagnetic states near half-filling in two dimensions.

Findings

Identification of saturated and non-saturated ferromagnetic phase transitions.

Discovery of two types of antiferromagnetic states near half-filling.

Observation of phase separation hiding a large electron mass AFM state.

Abstract

Ground state magnetic phase diagrams of the square and simple cubic lattices are investigated for the narrow band Hubbard model within the slave-boson approach by Kotliar and Ruckenstein. The transitions between saturated (half-metallic) and non-saturated ferromagnetic phases as well as similar transition in antiferromagnetic (AFM) state are considered in the three-dimensional case. Two types of saturated antiferromagnetic state with different concentration dependences of sublattice magnetization are found in the two-dimensional case in the vicinity of half-filling: the state with a gap between AFM subbands and AFM state with large electron mass. The latter state is hidden by the phase separation in the finite-U case.