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Various series expansions for a Heisenberg antiferromagnet model for SrCu$_2$(BO$_3$)$_2$

Zheng Weihong·C. J. Hamer·J. Oitmaa
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Abstract

We use a variety of series expansion methods at both zero and finite temperature to study an antiferromagnetic Heisenberg spin model proposed recently by Miyahara and Ueda for the quasi two-dimensional material SrCu$_2$(BO$_3$)$_2$. We confirm that this model exhibits a first-order quantum phase transition at T=0 between a gapped dimer phase and a gapless Néel phase when the ratio $x=J'/J$ of nearest and next-nearest neighbour interactions is varied, and locate the transition at $x_c=0.691(6)$. Using longer series we are able to give more accurate estimates of the model parameters by fitting to the high temperature susceptibility data.

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Zheng Weihong, C. J. Hamer, J. Oitmaa. 1998-11-03. Various series expansions for a Heisenberg antiferromagnet model for SrCu$_2$(BO$_3$)$_2$. https://doi.org/10.1103/physrevb.60.6608

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