Solution of a two leg spin ladder system

TL;DR

This paper introduces a solvable spin-1/2 ladder model using Bethe ansatz, revealing a phase transition at a critical rung coupling, advancing understanding of quantum spin systems.

Contribution

It presents a new exactly solvable spin ladder model mapped from the Hubbard model, identifying a critical point for phase transition.

Findings

Model is solvable via Bethe ansatz for all rung couplings.

A phase transition occurs at J_c=1/2 between gapped and gapless phases.

Mapping from Hubbard model with twisted boundary conditions is established.

Abstract

A new model for a spin 1/2 ladder system with two legs is introduced. It is demonstrated that this model is solvable via the Bethe ansatz method for arbitrary values of the rung coupling J. This is achieved by a suitable mapping from the Hubbard model with appropriate twisted boundary conditions. We determine that a phase transition between gapped and gapless spin excitations occurs at the critical value J_c=1/2 of the rung coupling.