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 J(0)-J(1)-J(2)-J(3) 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 J(0)+J(1) less than or equal to J(3). 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.