As escadas de Heisenberg de N pernas

Abstract

Compounds such as vanadyl pirophosphate (VO2)P2O7 and some cuprate systems (example: SrCu2O3 and Sr2Cu3O5) are experimental realizations of the Heisenberg ladders. These compounds are well known examples of strongly correlated systems. The physics of these systems is described, correctly, only by non-perturbative methods. In this work, we investigate the spin-S N-leg Heisenberg ladders using the density matrix renormalization group (DMRG) technique. We obtain estimates of the ground state energy per site, in thermodynamic limit (e∞), as well as of the spin gap (ΔS) for the ladders with spin up to S = 5/2 . We found that for half-integer spin ladders the spin gap is zero (finite) for N odd (even); whereas for the integer spin ladders our results support a finite spin gap, independent of the number of legs. These results are in agreement with the Haldane-Sierra s conjecture [1 3]. We also estimate the value of e∞ for the two-dimensional spin-S Heisenberg model from the ground state energies, in the thermodynamic limit, of the Heisenberg ladders.