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

Nonmagnetic impurities in an $S=1/2\mathrm{}$ Heisenberg antiferromagnetic chain are studied using boundary conformal field theory techniques and finite-temperature quantum Monte Carlo simulations. We calculate the static structure function, $S_{\mathrm{imp}}\left(k\right)$, measured in neutron scattering and the local susceptibility, ${\chi }_i$ measured in Knight shift experiments. $S_{\mathrm{imp}}\left(k\right)$ 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.