Zero-temperature study of a tetrameric spin-$1/2$ chain in a transverse magnetic field

TL;DR

This study investigates the zero-temperature quantum phase diagram of a tetrameric spin-1/2 chain under a transverse magnetic field, revealing five gapped phases, phase transitions, and entanglement signatures of these transitions.

Contribution

It introduces a detailed numerical analysis of how anisotropic ferromagnetic coupling induces new gapped phases and identifies quantum phase transitions using entanglement measures.

Findings

Identification of five gapped quantum phases.

Discovery of two new stripe-antiferromagnetic phases.

Entanglement measures verify quantum phase transitions.

Abstract

We consider an alternating Heisenberg spin-$1/2$ antiferromagnetic-ferromagnetic ($AF-F$) chain with the space modulated dominant antiferromagnetic exchange and anisotropic ferromagnetic coupling (tetrameric spin-$1/2$ chain). The zero-temperature effect of a symmetry breaking transverse magnetic field on the model is studied numerically. It is found that the anisotropy effect on the ferromagnetic coupling induces two new gapped phases. We identified their orderings as a kind of the stripe-antiferromagnetic phase. As a result, the magnetic phase diagram of the tetrameric chain shows five gapped quantum phases and the system is characterized by four critical fields which mark quantum phase transitions in the ground state of the system with the changing transverse magnetic field. We have also exploited the well known bipartite entanglement (name as concurrence) and global entanglement tools to verify the occurrence of quantum phase transitions and the corresponding critical points.