Spin gap and string order parameter in the ferromagnetic Spiral Staircase Heisenberg Ladder: a quantum Monte Carlo study

Abstract

We consider a spin-1/2 ladder with a ferromagnetic rung coupling J_\perp and inequivalent chains. This model is obtained by a twist (θ) deformation of the ladder and interpolates between the isotropic ladder (θ=0) and the SU(2) ferromagnetic Kondo necklace model (θ=π). We show that the ground state in the (θ,J_\perp) plane has a finite string order parameter characterising the Haldane phase. Twisting the chain introduces a new energy scale, which we interpret in terms of a Suhl-Nakamura interaction. As a consequence we observe a crossover in the scaling of the spin gap at weak coupling from Δ/J_\| \propto J_\perp/J_\| for θ< θ_c \simeq 8π/9 to Δ/J_\| \propto (J_\perp/J_\|)^2 for θ> θ_c. Those results are obtained on the basis of large scale Quantum Monte Carlo calculations.

4 pages

References in corpus (11)

• Surprises on the Way from 1D to 2D Quantum Magnets: the Novel Ladder Materials
• Bosonization and Strongly Correlated Systems
• Antiferromagnetic spin ladders: crossover between spin S = 1/2 and S = 1 chains
• The Loop Algorithm
• Cluster algorithms for general-S quantum spin systems
• The ALPS project: open source software for strongly correlated systems
• String order and adiabatic continuity of Haldane chains and band insulators
• Spin Gap in Chains with Hidden Symmetries
• A Luttinger Liquid Coupled to a Quantum Spin Bath: Flow Equation Approach to the Kondo Necklace Model
• Susceptibilities and Spin Gaps of Weakly-coupled Spin Ladders
• Centipede ladder at quarter filling

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• Generic short-range interactions in two-leg ladders
• Spin nematic states in antiferromagnets containing ferromagnetic bonds
• Spiral magnetism and chiral superconductivity in Kondo-Hubbard triangular lattice model
• Fractional spin excitations and conductance in the spiral staircase Heisenberg ladder