Quantum Monte Carlo Simulation of the Trellis Lattice Heisenberg Model for SrCu${}_2$O${}_3$ and CaV${}_2$O${}_5$

We study the spin-1/2 trellis lattice Heisenberg model, a coupled spin ladder system, both by perturbation around the dimer limit and by quantum Monte Carlo simulations. We discuss the influence of the inter-ladder coupling on the spin gap and the dispersion, and present results for the temperature dependence of the uniform susceptibility. The latter was found to be parameterized well by a mean-field type scaling ansatz. Finally we discuss fits of experimental measurements on SrCu${}_2$O${}_3$ and CaV${}_2$O${}_5$ to our results.