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Antiferromagnetic Heisenberg ladders in a staggered magnetic field

Jize Zhao·Xiaoqun Wang·Tao Xiang·Zhaobin Su·Lu Yu·Jizhong Lou·Changfeng Chen
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Abstract

We study the low-energy excitations of the spin-1/2 antiferromagnetic Heisenberg chain and $N$-leg ($N$=2, 3, 4) ladders in a staggered magnetic field $h_s$. We show that $h_s$ induces gap and midgap states in all the cases and examine their field scaling behavior. A modified boundary scheme is devised to extract accurate bulk excitation behavior. The gap values converge rapidly as $N$ increases, leading to a field scaling exponent $γ=1/2$ for both the longitudinal and transverse gaps of the square lattice ($N \to \infty$). The midgap states induced by the boundary edge effects share the bulk gap scaling exponents but their overall scaling behavior in the large-N limit needs further investigation.

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Jize Zhao, Xiaoqun Wang, Tao Xiang, Zhaobin Su, Lu Yu, Jizhong Lou, Changfeng Chen. 2005-11-21. Antiferromagnetic Heisenberg ladders in a staggered magnetic field. https://doi.org/10.1103/physrevb.73.012411

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