Phase separation in effective hard-core boson and triplet models in one and two dimensions

TL;DR

This paper derives and studies effective models of hole pairs and triplets in one and two dimensions, revealing phase separation characterized by hole-pair clouds and triplet expulsion, with implications for understanding correlated electron systems.

Contribution

It introduces effective hard-core boson and triplet models from the t-J model, highlighting phase separation phenomena in low-dimensional systems.

Findings

Hole pairs are surrounded by singlet clouds

Triplet excitations are expelled from hole-pair regions

Evidence of phase separation between singlet and triplet phases

Abstract

Effective models of hard-core hole pair bosons and triplets are derived from the t-J model in ladders and on the square lattice by performing a change from site to dimer basis. The Hilbert space is truncated by projecting out single-occupied electron states and only nearest neighbor interactions are retained. The resulting effective models in one and two dimensions are studied by numerical techniques. In both spatial dimensions, the main result is that each hole pair is surrounded by a singlet cloud expelling triplet excitations from its vicinity. It is suggested an interpretation of this feature as a phase separated state between a hole-pair rich singlet phase and an undoped triplet phase with antiferromagnetic correlations. The possible relevance of this result to other theoretical scenarios and experimental results is discussed.