Vanishing of the negative-sign problem of quantum Monte Carlo simulations in one-dimensional frustrated spin systems

We have solved the negative-sign problem in a general frustrated double-spin-chain system, namely the J₀-J₁-J₂-J₃ model. This is made possible by changing the representation basis from the conventional s^z basis to a dimer basis that has the spin-reversal symmetry. The necessary condition for the problem to disappear in this new basis is J₀+J₁≤J₃. Frustration is the origin only in the conventional s^z basis. We demonstrate the efficiency of this new basis at the transition point between the gapless spin-fluid phase and the gapped dimer phase.