Non-magnetic Impurities in Spin Gap Systems

TL;DR

This paper investigates how non-magnetic impurities affect spin gap systems, revealing that impurity-induced topological effects lead to enhanced antiferromagnetic correlations and more singular low-temperature behavior.

Contribution

It introduces a topological perspective on impurity effects in spin liquids, highlighting the role of Berry phases and decoherence in modifying magnetic properties.

Findings

Impurities induce a random Berry phase in the non-linear sigma model.

Antiferromagnetic correlations become more classical due to topological decoherence.

Staggered susceptibility exhibits more singular behavior at low temperatures.

Abstract

The effect of non-magnetic impurities is discussed for both the two-leg Heisenberg ladder system and other spin liquids with excitation gap. It is shown that the random depletion of spins introduces a random Berry phase term to the non-linear sigma model. The classical nature of the antiferromagnetic correlation is enhanced by the topological decoherence, and the staggered susceptibility shows more singular behavior at low temperatures than the uniform antiferromagnetic Heisenberg chain.