Antiferromagnetic Heisenberg ladders in a staggered magnetic field

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 $\gamma =1/2$ 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.

arXiv comment4 pages, 4 figures, to appear in Phys. Rev. B

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• Studying Two Dimensional Systems With the Density Matrix Renormalization Group
• Magnetization plateau in the S=1/2 spin ladder with alternating rung exchange
• The N-Leg spin-S Heisenberg ladders: A DMRG study
• Low-energy properties of anisotropic two-dimensional spin-1/2 Heisenberg models in staggered magnetic fields
• A semi-classical approach to electron spin resonance in quantum spin systems