Excitation Spectra and Thermodynamic Response of Segmented Heisenberg Spin Chains

Abstract

The spectral and thermodynamic response of segmented quantum spin chains is analyzed using a combination of numerical techniques and finite-size scaling arguments. Various distributions of segment lengths are considered, including the two extreme cases of quenched and annealed averages. As the impurity concentration is increased, it is found that (i) the integrated spectral weight is rapidly reduced, (ii) a pseudo-gap feature opens up at small frequencies, and (iii) at larger frequencies a discrete peak structure emerges, dominated by the contributions of the smallest cluster segments. The corresponding low-temperature thermodynamic response has a divergent contribution due to the odd-site clusters and a sub-dominant exponentially activated component due to the even-site segments whose finite-size gap is responsible for the spectral weight suppression at small frequencies. Based on simple scaling arguments, approximate low-temperature expressions are derived for the uniform susceptibility and the heat capacity. These are shown to be in good agreement with numerical solutions of the Bethe ansatz equations for ensembles of open-end chains.

arXiv commentRevTex, 9 pages with 6 figures

References in corpus (15)

• Surprises on the Way from 1D to 2D Quantum Magnets: the Novel Ladder Materials
• Susceptibility of the Spin 1/2 Heisenberg Antiferromagnetic Chain
• Coupled Ladders in a Magnetic Field
• Thermodynamics and spin gap of the Heisenberg ladder calculated by the look-ahead Lanczos algorithm
• Spin dynamics and transport in gapped one-dimensional Heisenberg antiferromagnets at nonzero temperatures
• Delocalization in coupled one-dimensional chains
• Spin-Peierls and Antiferromagnetic Phases in Cu{1-x}Zn{x}GeO{3}: A Neutron Scattering Study
• Local Enhancement of Antiferromagnetic Correlations by Nonmagnetic Impurities
• Random Quantum Spin Chains: A Real-Space Renormalization Group Study
• Low-Temperature Properties of the Randomly Depleted Heisenberg Ladder
• Enhancement of Antiferromagnetic Correlations Induced by Nonmagnetic Impurities: Origin and Predictions for NMR Experiments
• Logarithmic Corrections in Quantum Impurity Problems
• Low-Temperature Scaling Regime of Random Ferromagnetic-Antiferromagnetic Spin Chains
• Spin correlation functions in random-exchange s=1/2 XXZ chains
• Spectral Analysis of Correlated One-Dimensional Systems with Impurities

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• Bose glass behavior in (Yb${}_{1-x}$Lu${}_x$)${}_4$As${}_3$ representing the randomly diluted quantum spin-1/2 chains
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• Generation of spin-squeezed states using dipole-coupled spins