Brueckner approach to the spin-wave gap critical index for the two-layer Heisenberg antiferromagnet

P. V. Shevchenko, O. P. Sushkov

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10 Citations (Scopus)

Abstract

We consider the two-layer Heisenberg antiferromagnet near a zero-temperature quantum phase transition from a disordered dimer phase to a Néel state. At approaching the transition point the spin-wave gap vanishes as Δ∝(J-J⊥c)v. To account for strong correlations between the S= 1 elementary excitations we apply the Brueckner diagram approach which gives the critical index vπ0.5. We demonstrate also that the linearized in density Brueckner equations give the mean field result v= 1. Finally an expansion of the Brueckner equations in powers of the density, combined with the scaling hypothesis, give v≈0.67. This value reasonably agrees with that of the nonlinear O(3) σ model. Our approach demonstrates that for other quantum spin models the critical index can be different from that in the nonlinear σ model. We discuss the conditions for this to occur.

Original languageEnglish
Pages (from-to)8383-8386
Number of pages4
JournalPhysical Review B: Condensed Matter and Materials Physics
Volume59
Issue number13
Publication statusPublished - 1999
Externally publishedYes

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