Spin gaps in coupled<i>t</i>-<i>J</i>ladders
Spin gaps in coupled<i>t</i>-<i>J</i>ladders
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 …