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Quantum phase transitions in trimerized zig-zag spin ladders

H. D. Rosales·D. C. Cabra·M. D. Grynberg·G. L. Rossini·T. Vekua
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Abstract

We analyze the effects of a trimerized modulation in a quantum spin $S=\frac12$ 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.

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H. D. Rosales, D. C. Cabra, M. D. Grynberg, G. L. Rossini, T. Vekua. 2007-04-13. Quantum phase transitions in trimerized zig-zag spin ladders. https://doi.org/10.1103/physrevb.75.174446

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