arXiv:cond-mat/9810263 · Physical Review Letters

Massive and Massless Behavior in Dimerized Spin Ladders

D. C. Cabra, Marcelo D. Grynberg

Published Feb 22, 1999• 51 citations

Abstract

We investigate the conditions under which a gap vanishes in the spectrum of dimerized coupled spin-1/2 chains by means of Abelian bosonization and Lanczos diagonalization techniques. Although both interchain ( ${J}^{\ensuremath{'}}$) and dimerization ( $\ensuremath{\delta}$) couplings favor a gapful phase, it is shown that a suitable choice of these interactions yields massless spin excitations. We also discuss the influence of different arrays of relative dimerization on the appearance of nontrivial magnetization plateaus.

DOI: 10.1103/physrevlett.82.1768

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arXiv:cond-mat/9810263 · Physical Review Letters

Massive and Massless Behavior in Dimerized Spin Ladders

D. C. Cabra, Marcelo D. Grynberg

Published Feb 22, 1999• 51 citations

arXiv HTML PDF

Abstract

{J}^{\ensuremath{'}}

) and dimerization (

\ensuremath{\delta}

) couplings favor a gapful phase, it is shown that a suitable choice of these interactions yields massless spin excitations. We also discuss the influence of different arrays of relative dimerization on the appearance of nontrivial magnetization plateaus.

DOI: 10.1103/physrevlett.82.1768

Related papers

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We investigate the ground-state magnetization plateaus appearing in spin- $\frac{1}{2}$ two-leg ladders built up from dimerized antiferromagnetic Heisenberg chains and dimerized zig-zag interchain couplings. Using both Abelian bosonization and Lanczos methods we find that the system yields rather unusual plateaus and exhibits massive and massless phases for specific choices or ``tuning'' of exchange interactions. The relevance of this behavior in the study of ${\mathrm{NH}}_{4}{\mathrm{CuCl}}_{3}$ is discussed.We investigate the ground-state magnetization plateaus appearing in spin-$\frac{1}{2}$ two-leg ladders built up from dimerized antiferromagnetic Heisenberg chains and dimerized zig-zag interchain couplings. Using both Abelian bosonization and Lanczos methods we find that the system yields rather unusual plateaus and exhibits massive and massless phases for specific choices or ``tuning'' of exchange interactions. The relevance of this behavior in the study of ${\mathrm{NH}}_{4}{\mathrm{CuCl}}_{3}$ is discussed.

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Diego Mastrogiuseppe, C. J. Gazza, A. Dobry

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{J}^{\ensuremath{'}}

) and dimerization (

\ensuremath{\delta}

We investigate the ground-state magnetization plateaus appearing in spin-

\frac{1}{2}

two-leg ladders built up from dimerized antiferromagnetic Heisenberg chains and dimerized zig-zag interchain couplings. Using both Abelian bosonization and Lanczos methods we find that the system yields rather unusual plateaus and exhibits massive and massless phases for specific choices or ``tuning'' of exchange interactions. The relevance of this behavior in the study of

{\mathrm{NH}}_{4}{\mathrm{CuCl}}_{3}

is discussed.

\mathrm{XXZ}

chain in the presence of a magnetic field, which is then used for an Abelian bosonization analysis of

N

weakly coupled chains. Predictions for the universality classes of the phase transitions at the plateaux boundaries are obtained in addition to a quantization condition for the value of the magnetization on a plateau. These results are complemented by and checked against strong-coupling expansions. Finally, we analyze the strong-coupling effective Hamiltonian for an odd number

N

of cylindrically coupled chains numerically. For

N=3

we explicitly observe a spin gap with a massive spinon-type fundamental excitation and obtain indications that this gap probably survives the limit $\stackrel{\ensuremath{\rightarrow}}{N}\ensuremath{\infty}$.