Stability of homogeneous magnetic phases in a generalized t-J model

TL;DR

This paper investigates the stability of homogeneous magnetic phases in a generalized t-J model, revealing that Gaussian fluctuations destabilize certain magnetic orders despite mean-field stabilization.

Contribution

It introduces a detailed analysis of magnetic phase stability in a generalized t-J model including fluctuation effects beyond mean-field approximation.

Findings

Mean-field order stabilizes spiral and Neel phases against phase separation.

Gaussian fluctuations induce instabilities in magnetic phases.

Reduced stability regions for Neel order are identified.

Abstract

We study the stability of homogeneous magnetic phases in a generalized t-J model including a same-sublattice hopping t' and nearest-neighbor repulsion V by means of the slave fermion-Schwinger boson representation of spin operators. At mean-field order we find, in agreement with other authors, that the inclusion of further-neighbor hopping and Coulomb repulsion makes the compressibility positive, thereby stabilizing at this level the spiral and Neel orders against phase separation. However, the consideration of Gaussian fluctuation of order parameters around these mean-field solutions produces unstable modes in the dynamical matrix for all relevant parameter values, leaving only reduced stability regions for the Neel phase. We have computed the one-loop corrections to the energy in these regions, and have also briefly considered the effects of the correlated hopping term that is obtained in the reduction from the Hubbard to the t-J model.