Gap's in the antiferromagnetic Heisenberg model

1998/09/04 by A. Fledderjohann, Fledderjohann, A., M. Karbach +3
Physics and Astronomy · #FOS: Physical sciences #Strongly Correlated Electrons (cond-mat.str-el) #cond-mat.str-el

paper · pdf · doi:10.48550/arxiv.cond-mat/9809086

7 pages, 6 figures, LaTeX-class svjour from Springer; to be published in Eur. Phys. J. B

arxiv created 1998/09/04 · arxiv updated 2009/11/30

Abstract

We study the one-dimensional spin-1/2 antiferromagnetic Heisenberg model exposed to an external field, which is a superposition of a homogeneous field h₃ and a small periodic field of strength h₁. For the case of a transverse staggered field a gap opens, which scales with h₁^ε₁, where ε₁=ε₁(h₃) is given by the critical exponent η₁(M(h₃)) defined through the transverse structure factor of the model at h₁=0. For the case of a longitudinal periodic field with wave vector q=π/2 and strength h_q a plateau is found in the magnetization curve at M=1/4. The difference of the upper- and lower magnetic field scales with h₃^u-h₃^l∼ h_q^ε₃, where ε₃=ε₃(h₃) is given by the critical exponent η₃(M(h₃)) defined through the longitudinal structure factor of the model at h_q=0.

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