Long-range spin-pairing order and spin defects in quantum spin-1/2 ladders

TL;DR

This paper investigates the long-range spin-pairing order in antiferromagnetic spin-1/2 ladders, revealing degeneracy patterns, symmetry breaking, and the effects of topological defects, providing a systematic understanding of even and odd ladder differences.

Contribution

It introduces a classification of valence-bond configurations into subspaces and explains degeneracy and symmetry breaking in spin ladders systematically.

Findings

Long-range spin-pairing order enables subspace classification.

Degeneracy and symmetry breaking depend on ladder parity.

Topological spin defects cause discontinuities in order.

Abstract

For w-legged antiferromagnetic spin-1/2 Heisenberg ladders, a long-range spin-pairing order can be identified which enables the separation of the space spanned by finite-range (covalent) valence-bond configurations into w+1 subspaces. Since every subspace has an equivalent counter subspace connected by translational symmetry, twofold degeneracy, breaking traslational symmetry is found except for the subspace where the ground state of w=even belongs to. In terms of energy ordering, (non)degeneracy and the discontinuities introduced in the long-range spin-pairing order by topological spin defects, the differences between even and odd ladders are explained in a general and systematic way.