Phase diagram of an asymmetric spin ladder - art. no. 087205

We investigate an asymmetric zigzag spin ladder with different exchange int egrals on both legs using bosonization and renormalization group approaches . When the leg exchange integrals and frustration both are sufficiently sma ll, renormalization group analysis shows that the Heisenberg critical point flows to an intermediate-coupling fixed point with gapless excitations and a vanishing spin velocity. When they are large, a spin gap opens and a dim er liquid is realized. Here, we find a continuous manifold of Hamiltonians with dimer product ground states, interpolating between the Majumdar-Ghosh and sawtooth spin-chain model.