Low-energy properties of antiferromagnetic spin-1/2 Heisenberg ladders with an odd number of legs

An effective low-energy description for multileg spin-1/2 Heisenberg ladders with an odd number of legs is proposed. Using a recently developed Monte Carlo loop algorithm and exact-diagonalization techniques, the uniform and staggered magnetic susceptibility and the entropy are calculated for ladders with one, three, and five legs. These systems show a low-temperature scaling behavior similar to spin-1/2 chains with longer ranged unfrustrated exchange interactions. The spinon velocity does not change as the number of legs increases, but the energy scale parameter decreases markedly.