Impurities in S=1/2 Heisenberg Antiferromagnetic Chains: Consequences for Neutron Scattering and Knight Shift

TL;DR

This paper investigates how non-magnetic impurities affect the magnetic properties of S=1/2 Heisenberg antiferromagnetic chains, impacting neutron scattering and Knight shift measurements through theoretical and simulation methods.

Contribution

It introduces a combined boundary conformal field theory and quantum Monte Carlo approach to analyze impurity effects in quantum spin chains.

Findings

Impurity-induced static structure function S_imp(k) peaks near the antiferromagnetic wave-vector.

S_imp(k) shows stronger temperature dependence than the bulk structure function.

Local susceptibility chi_i exhibits alternating behavior and increases with distance from impurities.

Abstract

Non-magnetic impurities in an S=1/2 Heisenberg antiferromagnetic chain are studied using boundary conformal field theory techniques and finite-temperature quantum Monte Carlo simulations. We calculate the static structure function, S_imp(k), measured in neutron scattering and the local susceptibility, chi_i measured in Knight shift experiments. S_imp(k) becomes quite large near the antiferromagnetic wave-vector, and exhibits much stronger temperature dependence than the bulk structure function. \chi_i has a large component which alternates and increases as a function of distance from the impurity.