Spin Gaps in Coupled t-J Ladders

Abstract

Spin gaps in coupled $t$-$J$ ladders are investigated by exact diagonalization of small clusters up to 4$\times$8 sites. At half-filling, the numerical results for the triplet excitation spectrum are in very good agreement with a second order perturbation expansion in term of small inter-ladder and intra-ladder exchange couplings between rungs ($J/J^{\prime }$$<$$0.25$). The band of local triplet excitations moving coherently along the ladder (with momenta close to $\pi$) is split by the inter-ladder coupling. For intermediate couplings finite size scaling is used to estimate the spin gap. In the isotropic infinite 4-chain system (two coupled ladders) we find a spin gap of $0.245J$, roughly half of the single ladder spin gap. When the system is hole doped, bonding and anti-bonding bound pairs of holes can propagate coherently along the chains and the spin gap remains finite.

11 pages, 5 figures, uuencoded form of postscript files of figures and text, LPQTH-94/5

References in corpus (5)

• Spin-ladders with spin gaps: A description of a class of cuprates
• Superconductivity in a Quasi One Dimensional Spin Liquid
• Pairing and Excitation Spectrum in doped t-J Ladders
• Binding of holes and pair spectral function in the t-J model
• On the Internal Structure of the Singlet d${}_{X^2-Y^2}$ Hole Pair in an Antiferromagnet

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