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arXiv · 1603.04362

Properties of the random-singlet phase: from the disordered Heisenberg chain to an amorphous valence-bond solid

Yu-Rong Shu·Dao-Xin Yao·Chih-Wei Ke·Yu-Cheng Lin·Anders W. Sandvik
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Abstract

We use a strong-disorder renormalization group (SDRG) method and ground-state quantum Monte Carlo (QMC) simulations to study S=1/2 spin chains with random couplings, calculating disorder-averaged spin and dimer correlations. The QMC simulations demonstrate logarithmic corrections to the power-law decaying correlations obtained with the SDRG scheme. The same asymptotic forms apply both for systems with standard Heisenberg exchange and for certain multi-spin couplings leading to spontaneous dimerization in the clean system. We show that the logarithmic corrections arise in the valence-bond (singlet pair) basis from a contribution that can not be generated by the SDRG scheme. In the model with multi-spin couplings, where the clean system dimerizes spontaneously, random singlets form between spinons localized at domain walls in the presence of disorder. This amorphous valence-bond solid is asymptotically a random-singlet state and only differs from the random-exchange Heisenberg chain in its short-distance properties.

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Yu-Rong Shu, Dao-Xin Yao, Chih-Wei Ke, Yu-Cheng Lin, Anders W. Sandvik. 2016-03-14. Properties of the random-singlet phase: from the disordered Heisenberg chain to an amorphous valence-bond solid. https://doi.org/10.1103/physrevb.94.174442

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