Quantum phase transitions in trimerized zig-zag spin ladders

Abstract

We analyze the effects of a trimerized modulation in a quantum spin $S=\frac{1}{2}$ zig-zag ladder at the magnetization plateau $M=1/3$. Such periodicity is argued to be stemmed from lattice deformations by phonons. The interplay between frustration and exchange modulation is well described by an effective triple sine-Gordon field theory close to the homogeneous ladder and by block-spin perturbation theory in the weakly coupled trimers regime. The characteristic triple degeneracy of the ground state for homogeneous ladders gives place to modulation driven quantum phase transitions, leading to a rich phase diagram including up-up-down, quantum plateau and gapless plateau states.

Numerical analysis improved, 4 figures added. Final version to appear in Phys. Rev. B

References in corpus (3)

• Magnetic phase diagram of the S=1/2 antiferromagnetic zigzag spin chain in the strongly frustrated region: cusp and plateau
• Frustrated three-leg spin tubes: from spin 1/2 with chirality to spin 3/2
• Quantum vs. Classical Magnetization Plateaus of S=1/2 Frustrated Heisenberg Chains